In trying to solve a couple of problems from a game I recently played, I took another look at action economy. I came up with something I haven't tested but I kinda like. It turns out you folks like to talk about this stuff, so I thought I'd throw it on the wall and let you shoot it full of holes.
Characters get 10 Action Points per round
- Standard human movement is 6' per AP (so 1 square per AP until you move 5, then you get +1 square)
- Dwarfy movement is 4' per AP (so 1 square per AP until you move 3, then it costs 2 AP to move the next square)
- Casting most spells costs 6 AP
- Weapons have a speed quality. Standard is 5, faster and slower weapons vary by +/-1
- Attacking costs a number of AP equal to your weapon's speed, and attacking multiple times during a round never results in an attack bonus penalty
- TWF grants you an extra attack with the off-hand weapon at -2 AP cost for that attack, and you can only attack with the off-hand weapon after you've made a main-hand attack (so 2 dagger attacks is 6AP, the same as one greataxe attack)
- Spells like haste give you bonus AP
- Some feats increase the efficiency of weapon speed, and quicken spell reduces the AP cost of the affected spell
- A 5' step is done more like the shift in 4e - it still costs 1AP but if it's your only movement it doesn't provoke
- 1 AP = 2 initiative rank; You can spend leftover AP at the end of your turn to improve your initiative or you can lower your initiative to gain extra AP, both are up to 2 AP per round and you cannot drop your initiative to less than 0
- Higher BAB only affects your attack bonus, not AP cost for attacks
- Natural attacks follow exactly the same rules as weapons, no exceptions
- A level 20 monk makes unarmed strikes at a cost of 1 AP per attack when flurrying (as a benchmark example)
- Other "move" etc actions like drawing a weapon need to be defined
- Casting spells makes you less mobile, with only 4AP left for movement.
- This system makes initiative more dynamic, which is a strong feature.
- Using big weapons is more difficult than using smaller weapons. You CAN make 2 attacks with a greataxe every round, but only by dropping 4 initiative points per round. This makes improved initiative even better, by granting effectively a +2 buffer to the total extra AP that can be gained by lowering your initiative. A downside to this is that if your enemies all get better initiative than you, there's little reason not to burn initiative to get extra AP - in fact the only reason not to is to position yourself in initiative such that if the enemy does this you go before him.
- Fighting with two weapons is viable even without the TWF feat - using a one-handed standard weapon with an off-hand faster weapon is possible if you don't move. Math time: longsword + dagger w/18 Str = 1d8+4+1d4+2=13 average (with 1 AP left over for movement). Greataxe w/18 Str = 1d12+6=12.5 average (with 4 AP left over for movement).
- Getting the same number of attacks normally allotted to a character with a very high BAB is only possible through stacking of spells, feats, and other tricks, which at high levels are probably very easy to get. The downside of this is that physical combatants aren't given as many options at high levels, but it does get rid of the "Full attack action or I suck" problem.
- The ease of getting 2 spells off in a round (by taking a -4 hit to initiative rank) is an unintended negative consequence. It may be worth limiting spells to 1 per round no matter what, allowing only quickened spells to bypass this. Quickened spells should probably be more flexible, costing an additional spell level for every 1 point of AP reduction (so if you want to spend all 10 AP for the round, cast a normal spell and a quickened spell with a +2 spell level adjustment).
- After coming up with this and talking to a friend he mentioned that it sounds similar to Exalted, so I played that (it's awesome, in its own way) and found that my fear that keeping track of AP would result in too much bean counting is probably unfounded. Also, this isn't complicated so it's easier to learn and use than 3.x's normal action system (noob is right, it's not easier to learn).