I was brainstorming for some ideas, when I looked at the vigor and wounds system that Paizo offered, and I got a weird idea.
It's this: Every class has a pool of Effort(need help with the name) points, which is made of half their total hit die plus their Con modifier.
It's Con because this represents physical exhaustion.
This pool represents the effort it takes for the character to take blows, or roll with them, etc. Basically, the first points of damage drain from the Effort Points, not regular HP. Once that is gone, they start receiving hit point damage as normal. However, unlike normal hit points, the class regenerates a number of Effort points equal to their Con modifier, minimum +1 of course. I guess I should tweak that number, maybe make up a feat or something that gives you a larger pool, or speeds up the regenerating. Let's move on.
For the martial classes, this pool won't really matter; basically being an extra bunch of hit points that replenish themselves. It gets more interesting when you apply it to casters.
Casting a spell will drain points from the caster (Because I am a firm believer that casting a spell should take some freaking effort, and the thin-as-a-stick elf shouldn't lift 500+ lbs rocks without breaking a sweat). It will drain as much points as the effective spell level. This hopefully will prevent casters from going nova, and force them to conserve spells in battle.
Apologies, but I couldn't find a better way to explain this part without an example.
If someone has 2 Effort points left, and he is hit for 15 damage, he receives 13 points of damage and the pool is completely drained.
Also, if a caster would cast a spell that would bring his pool down to negatives, he receives twice that spell's effective level in nonlethal damage and becomes fatigued. He can continue to strain himself until he falls unconscious. If he repeats this, he becomes exhausted. Again, and he falls unconscious.
Level 5 wizard with 14 con has a pool of 4. He can cast 2 third level spells, in two rounds without hurting himself.
If we go with this system, it is also possible to add little balancing tweaks, such as sorcerers not spending as much points (representing their natural talent) or maybe certain classes adding other modifiers, like the Monk adding his Wis to the points replenished each round.
So how does it look? Stupid? Pointless? Complicated? Please let me know.
Personally, I'd go with a system to make the Monk/Fighter/Barbarian do cool things- blow an effort point to move 10 feet, gain DR/- equal to 1/2 your level until the start of your next turn, add +30 on a strength or dexterity based skill check, heal a certain amount, Stuff like that. It makes those particular characters more interesting to play rather than charge/full-attack. Give a certain amount each day (1/2 level + Con isn't bad) to characters without spells, then just detail the effects that they can use. It still won't make things like the monk or fighter anywhere near as powerful, but it'll power them up a little bit. It also has the benefit of making the less interesting classes more interesting.
The biggest problem with your idea that I see is that it's more punitive to the caster at lower levels than it is at higher levels. The high level wizard only needs to cast a couple spells each combat anyway, and a lot of the time can cast 1 spell to wreck the field overall, so the limitation on the amount of points they have (a 10th level wizard that started with 14 Con can easily get 18, putting them at 9 points and a 4 gain, meaning they can cast a pair of level 6 spells in 2 turns and still have points left over) isn't much of a limitation at all.
The idea is solid, and if implemented right, could limit it fairly well, but as-is, the math starts breaking down at higher levels.
Level 20 Wizard. Started with 14 con, picked up a +6 belt, +5 from Wish, +1 from a level up bonus has 26 Con (+8 modifier). He has 18 points and regains 8 per round. Unless he's getting ganged up on (unlikely because he's a wizard), he can cast 8th level spells without any issues, and can toss out 9th level spells regularly. There is no change in this from a wizard of 20th level. All he gets is a bonus 18 hp, not much when a beastie can smack you around for 100 points of damage or so.
Seems overly complicated and adds another resource to track. Not to mention it punishes certain already inefficient builds (blasters) while rewarding encounter breaking builds (SoS casters only need 1 or 2 spells cast in an encounter).
I was brainstorming for some ideas, when I looked at the vigor and wounds system that Paizo offered, and I got a weird idea.
I played with a similar variant hp rule years ago, whereas every character had an equal pool of points (regardless of class) to absorb damage (parries and dodges)and fuel spells, and a separate pools of points representing how much physical damage they could take before dying. Here are the two mains observations I made.
1) Casters got really stingy with their spellcasting, as every spell brought them effectively more exposed to a killing blow.
2) It was frustrating for caster to receive hits. "That's 28 damage." "Well, I guess I won't be casting all these spells here then..."
There's more to it but in the end, we dropped because it was sort of a catch-22 for spellcasters that caused more frustration than anything else.
The idea has merit, but my experience tells me that it isn't portable to Pathfinder without serious reconstruction of the whole system.
'findel