ashockney said:
I'd throw this question out to anyone who plays a traditional D&D campaign (mostly combat to earn xp), and use more books than the core rules: anyone in your campaign play a bard recently? How about a fighter - straight up? Hmmm... Curious.
The reason I chose to tackle the items on this list together is to because of the synergy I found when trying to playtest solutions to some of them. Good fixes to one, had a positive carryover effect to the others.
A couple of examples: get rid of polymorph, get rid of books of stat buffs, simplify the morale, size, competence, luck, insight, and size bonuses and buffs.
Speeding up high level play, two words: use averages.
I played a bard awhile ago. She was individually weak (mostly by design) but an effective force multiplier. Ultimately, the biggest problem with the character was that I'm not good at all coming up with dialogue spontaneously. Therefore, many times my character's excellent social skills (18 CHA plus most of my skill points) went wasted. In our current game, a member of our rival group is bard. As a member of the NPC party, he's been fairly effective, combing effective, cheap group buffs with several incapacitating and hindering spells. Of course, that situation neglects several factors: his bard skills and some aspects of his bardic music don't really come into play since PCs are immune to persuasion out of combat, and they don't work in combat. On the other hand, since they only have effectively one battle a day (us), the bard's extremely low spell/day aren't major concern - after hitting out group with glitterdust, suggestion, and tasha's, a bard is pretty much out of second level spells. Even though he really nailed us in that fight, he'd have nothing left for later in the day.
The utility of going straight fighter is mostly dependent on how many feats your fighting style can support. There aren't really that many core feats for a two hander specialist to take. Using 2 weapons takes a lot of feats, especially if your shield is your off hand weapon. Something like a spiked chain can use tons of feats. Since the only real feature the fighter class offers (besides bab, HP, etc) is feats, then once the good feats run out, or nearly run out, there's not much reason to continue in the class. But a spiked chain master, or a character using a weapon supporting a number of feat chains, can probably stay fighter almost all the way - the spiked chain guy will probably be tempted away from fighter for a level or two to pick up Exotic Weapon Master.
One thing to consider about simplifying high level combat is that you don't want to do so to the extent that the tactical and strategic considerations become less important. Also, presumeably, DMs and players have had lower levels to prepare for the complexity of higher levels. Characters will have had many of their high level abilities for quite some time and so the players should be used to them.
Some of things you mentioned are actually rather simple. For example, stat buffing books. Very few other effects offer inherent bonuses; stacking considerations are essentially nil. Since the effects are permanent, there are no changes in play to be considered. It slows down play about as much as stat increases every 4 levels.
Of course, there is room to simplify and speed things up. One thing that can slow things down is situational or specialized bonuses. Something like +1 AC against 1 guy, or +2 versus charms is a mess because you can't add the bonus in to normal saves or AC and thus need to remember to apply it each time. Individually, this is no big deal, but combine several specific effects which may or may not apply - especially when dealing with possibly unknown factors, like the subtype of a specific spell or monster - and things get complex and a bit unweildy. Bonuses that apply all the time can just be noted on the sheet without having to compare descriptors.
Another issue is that stats are highly dynamic. While a fully buffed character is going to have bigger bonues, once you arrive at the total bonus, it doesn't really matter how much of that is luck/insight/whatever. All the stacking issues can be easily dealt with ahead of time, or by the people who use the spells all the time and remember what they do. Attacking 10 points higher then normal due to a bunch of buff spells isn't really more complex. The complexity comes in when the PC is between unbuffed and fully buffed states. For example, my cleric normally attacks at +18/+13, and attacks at +26/+26/+21/+16 when fully buffed. The difference is one more die roll. But when the character is dispeled, ambushed, or uses spells of such short duration that he'll cast them quickened while attacking, then we have a number of possible situations which can't really be economically precalculated. The ability to polymorph into anything or summon a bunch of different monsters will similarly slow things down - summoning in particular. Not only is another combatant added to the fray, but players and DMs will likely be less familar with the abilities of weird summoned stuff.
Finally, player choice is the last big slow down. Spellcasters are probably the worst higher, but if players are fanatics about trying to squeeze every last drop of damage out of power attack and stuff, then fighters slow things down too. At high levels, casters will probably have between 5 and 20 good spells to employ most rounds. The area or targets of the spell need to be selected. The caster probably has metamagic items which he chooses to use or not use; some of which may involve casting another spell. Then there's the strategic consideration about saving spells for later. Finally, some casters, namely clerics, will have the option of making effective attacks too, so they have to weigh casting versus attacking. There are really only two solutions here, and the first one is to take away options - not exactly the ideal move.