If I may interfere;
I tried taking Sneer's idea and run with it. I liked what he came up with. After awhile it came down to this:
- There are 7 scales: Str, Dex, Con, Int, Wis, Cha & hp.
- Each scale has 5~6 steps: buffed->normal->debuffed(1st)->debuffed(2nd)->debuffed(3rd)->death.
- This resembles SAGA scale and have the numeric values of [+2, 0, -2, -5, -10, -].
- An ability that buffs move you one step left, an ability that debuffs moves you one step right.
- Apart from numeric value, the scale steps are codified and are used for conditions dependencies (e.g. you can't fly into rage unless you're debuffed on the hp scale).
- Saves are never changed by this buffs (to prevent death spiral), and the 3rd bad step is temporary, after few rounds or when the combat is over it moves automatically to debuffed(2nd).
- I tried having a positive 3 steps as well but I kept having the players work more to gain buffs then attacking (for me it was annoying - but that's very subjective).
You could read it in the Abilities link down below.
Unfortunately, my group didn't have any more get togethers for a long time. So I wasn't able to test it further.