Basically, you want a kind of system that allows you to do interesting stunts, but they happen not all the time. So you must create limitations. 4E limitation is "once per encounter", "once per day".
3E limitations were typically a strong innate drawback to each option:
- Provokes AoO
- You take a penalty to the roll
- A specific condition or sequence of actions is required (tactical feats)
- You no longer can use a non-light weapon (grapple)
- You lose your Dex Bonus (grapple, run)
- The attack can be countered and used against you (Disarm, Trip)
The Book of Iron Might introduces a lot more options in this regard, basically all based on mixing penalties and drawbacks to allow you varied options.*
This is more convoluted. Basically every time you consider your options, you have to check if any specific conditions allowing you an option apply, what penalties do apply, and if you do actually provoke (based on the option you consider and the scenario). The more options you actually have, the longer the decision making process will take.
4E approach works the other way around - you check if you have used this power recently, and then apply its rules. That's still a type of convoluted approach, but the "hard" decision making is done faster and the implementation is what takes time - you don't have to do all in one step, and if you consider multiple options, this can make a difference.
In both cases, you still have to add tactical considerations (3E: Should I really risk an AoO from the enemy Fighter to disarm him? 4E: Should I use a Close Burst 1 power if there are only two enemies adjacent to me?), which of course make things take longer. (But this is usually also an interesting part of the decision making process - figuring out if a course of action is a good idea, not if it's even possible)
Iron Heroes tried to abstract these by just having tokens […]
I am not saying that the 4E approach is the best approach possible. I am saying that every design will have to make tradeoffs. You gain in "usability", you lose in believability. You make things faster, you have less options. […]
There are no perfect solutions. You have, at some point, make "sacrifices" or set your priorities.