I should make clear that I really, really like Trailblazer. It presents the best 3.x I've ever seen, and (to the limits of my understanding), I agree with the design philosophy.
However, 3.x had significant problems. One of the biggest is that it's a very complicated game. Teaching new players, or retraining old ones, is difficult. The main reason for that is not the array of options, as narrowing down what kind of options are preferable isn't too hard, but the array of rules. It wouldn't matter if the core rules had 7 classes or 49, so long as it was easy enough to ask a newbie, "What kind of hero do you want to play?" and translate their answer into one or two character classes. What does matter is how many pages of system rules a new player has to assimilate, especially those that deal with special cases. Think of that as a "stuff/rules" distinction: stuff that you can take or leave isn't a problem, while the rules with which you're stuck will be one.
So, here's a kind of review of Trailblazer's player section, focusing on this important distinction:
Introduction
Most of this is game theory and essential to the book's mission. The rules are Resting, Iterative Attacks, and Action Points. Only the last of these is significantly complex, and it's not really that hard.
Character Creation
This is an important section, and most of the rules in it are essential to the basic functioning of the game. Frankly, I recommend removing races altogether. The designer admits that they make very little difference to character balance. However, races add complexity to character creation without adding much flavor. To compensate, add an extra feat for all characters at 1st or 0th level. Skill points have already been increased.
There are two other existing mechanics that can deal with racial differences. When we're talking about "standard" races and cultures, it makes most sense to make one of the 1st level feats an "origin" feat and provide options in this vein. For "non-standard" races, race-as-class is the best option. (Race-as-class was smuggled in the back door of 3e, after all.) Just what counts as "standard" should vary from campaign to campaign. In Basic, Elves and Dwarves were "non-standard", while from Advanced onwards, they became "standard". Humans have - up to now - been a "standard" option.
Character Classes
All that a new player needs to know to navigate this section is a quick run-down on the 11 different classes. It might be slightly difficult to explain the difference between a sorcerer and a wizard, but that's not worth a change.
Skills
This section consists of 22 pages of rules, many of the hand-holding or smothering variety. The problems are not original to Trailblazer, and the designer has clearly worked to improve the system. The addition of exploits is a good one, however, it's not well described in the core skill section.
By the way, there are a number of 3rd edition skills which have actually worsened the game. Search is the most despicable. The Grognards used a description of how their characters interacted with the environment to determine success. We seem to just roll dice. Knowledge skills are also pretty bad. They've hurt the bard, marginalized interactions with sages, and seem to exist mainly due to a fear of metagaming. (As if that could be stopped by rules!) I don't have any problem with Persuasion and its ilk. Asking players to think carefully about how their characters explore a dungeon is a reasonable expectation of the hobby (immersion). Eloquence and force of personality are not required, and can often be the trademarks of a problem player. Wallflowers are welcome to play great diplomats, just as those of you who can't cast spells get to be wizards - but in both cases, the player is the one doing the thinking.
This section would be best dealt with by using its first three or four pages to describe a generic skill resolution system, and then merely describing what specific skills do, with example DCs if necessary, rather than giving a specific system for each one. I would ditch Search and all Knowledges. The page count should end up as 4 pages of general system. Each skill can be introduced in a couple of paragraphs (no system is strictly necessary, though briefly stating example DCs and exploits would help players and refs).
Feats
This is a similar section to that for classes. It would be helpful for new players if more feats were typed (e.g. "Defense", "Weapon"). Some of the feats are organically combined with certain combat or skill options, and need to be eliminated. It would be more help to players to give them a "signature maneuver" feat template in the same vein as weapon specialization.
Equipment
Another section full of stuff, and starving demihumans.
Combat
There are 33 pages of rules for combat - too many! Most of the page count comes from specialized rules. As a consequence, specialized solutions are necessary to trim it down.
Exploration
As a matter of taste, this chapter should be put before Combat. Use Rope could perhaps be simplified, but there are no significant problems.
Magic
Not having the spell descriptions makes it clear that d20's magic rules were fairly simple. I don't see much room for abbreviating what's here.
However, 3.x had significant problems. One of the biggest is that it's a very complicated game. Teaching new players, or retraining old ones, is difficult. The main reason for that is not the array of options, as narrowing down what kind of options are preferable isn't too hard, but the array of rules. It wouldn't matter if the core rules had 7 classes or 49, so long as it was easy enough to ask a newbie, "What kind of hero do you want to play?" and translate their answer into one or two character classes. What does matter is how many pages of system rules a new player has to assimilate, especially those that deal with special cases. Think of that as a "stuff/rules" distinction: stuff that you can take or leave isn't a problem, while the rules with which you're stuck will be one.
So, here's a kind of review of Trailblazer's player section, focusing on this important distinction:
Introduction
Most of this is game theory and essential to the book's mission. The rules are Resting, Iterative Attacks, and Action Points. Only the last of these is significantly complex, and it's not really that hard.
Character Creation
This is an important section, and most of the rules in it are essential to the basic functioning of the game. Frankly, I recommend removing races altogether. The designer admits that they make very little difference to character balance. However, races add complexity to character creation without adding much flavor. To compensate, add an extra feat for all characters at 1st or 0th level. Skill points have already been increased.
There are two other existing mechanics that can deal with racial differences. When we're talking about "standard" races and cultures, it makes most sense to make one of the 1st level feats an "origin" feat and provide options in this vein. For "non-standard" races, race-as-class is the best option. (Race-as-class was smuggled in the back door of 3e, after all.) Just what counts as "standard" should vary from campaign to campaign. In Basic, Elves and Dwarves were "non-standard", while from Advanced onwards, they became "standard". Humans have - up to now - been a "standard" option.
Character Classes
All that a new player needs to know to navigate this section is a quick run-down on the 11 different classes. It might be slightly difficult to explain the difference between a sorcerer and a wizard, but that's not worth a change.
Skills
This section consists of 22 pages of rules, many of the hand-holding or smothering variety. The problems are not original to Trailblazer, and the designer has clearly worked to improve the system. The addition of exploits is a good one, however, it's not well described in the core skill section.
By the way, there are a number of 3rd edition skills which have actually worsened the game. Search is the most despicable. The Grognards used a description of how their characters interacted with the environment to determine success. We seem to just roll dice. Knowledge skills are also pretty bad. They've hurt the bard, marginalized interactions with sages, and seem to exist mainly due to a fear of metagaming. (As if that could be stopped by rules!) I don't have any problem with Persuasion and its ilk. Asking players to think carefully about how their characters explore a dungeon is a reasonable expectation of the hobby (immersion). Eloquence and force of personality are not required, and can often be the trademarks of a problem player. Wallflowers are welcome to play great diplomats, just as those of you who can't cast spells get to be wizards - but in both cases, the player is the one doing the thinking.
This section would be best dealt with by using its first three or four pages to describe a generic skill resolution system, and then merely describing what specific skills do, with example DCs if necessary, rather than giving a specific system for each one. I would ditch Search and all Knowledges. The page count should end up as 4 pages of general system. Each skill can be introduced in a couple of paragraphs (no system is strictly necessary, though briefly stating example DCs and exploits would help players and refs).
Feats
This is a similar section to that for classes. It would be helpful for new players if more feats were typed (e.g. "Defense", "Weapon"). Some of the feats are organically combined with certain combat or skill options, and need to be eliminated. It would be more help to players to give them a "signature maneuver" feat template in the same vein as weapon specialization.
Equipment
Another section full of stuff, and starving demihumans.
Combat
There are 33 pages of rules for combat - too many! Most of the page count comes from specialized rules. As a consequence, specialized solutions are necessary to trim it down.
- Remove attacker and defender modifier tables. Just advise the ref to think about applying +2/-2 modifiers to attack rolls and armor classes to represent advantages and disadvantages.
- Remove initiative rules. Instead, the ref determines which side has the initiative (based on their position, preparedness, agility, etc). They act first, followed by the other side. If the ref can't make up his mind, flip a coin or roll a die to determine who starts. This eliminates the often misunderstood Delay and Ready actions.
- It should be made clear that the stated Combat Reactions are examples, not an exhaustive list. Aid probably just needs a single entry.
- The section on Movement, Position and Distance should be part of an expanded optional rules section for using miniatures. They are fun. I'm not against them. But they're not core to the game.
- Attack and Defense exploits are not similar to Skill exploits. It would be more help to the ref to have these sorts of things used as examples for using the +2/-2 tool in combat. In the same way, the favorable and unfavorable conditions section can be reduced to a phrase or two.
- Charging is a +2/-2 situation. The rules for lances and pike-type weapons can be left in the equipment section as suggestive.
- Turn or Rebuke Undead should be in the cleric class description, just as Sneak Attack is in the rogue class description.
- Combat Maneuvers. The standardization is good, but the position in the rules is awkward. It would be better to introduce CMB & CMD earlier in the chapter. Most players and refs will get the idea from short examples (Sunder and Trip - no system, just the idea that you can do this sort of thing with a Combat Maneuver).
- Grappling remains a problem, despite the designer's efforts. As an example: the rules as written imply that the Intimidate skill can't be used while Pinning an Opponent. That's absurd, and it illustrates the difficulty with trying to idiot-proof rules - folly can be great fun! I think the best way to deal with this is to simply explain that some Combat Maneuvers involve contested CMB checks, rather than using CMB against CMD, and use grappling as the example (again, with little or no system).
- The conditions grappled, pinned, and prone would all be removed as a consequence of this approach.
Exploration
As a matter of taste, this chapter should be put before Combat. Use Rope could perhaps be simplified, but there are no significant problems.
Magic
Not having the spell descriptions makes it clear that d20's magic rules were fairly simple. I don't see much room for abbreviating what's here.