So we allow buffs and debuffs of the same type to "stack" with each other? In that case I am guessing buffs of one type still do not stack with buffs of the same type, and likewise for debuffs. If thats the case I think it would be easier to think of it as 6 categories, where you have your magic buff, magic debuff, morale buff, morale debuff, circumstance buff, and circumstance debuff.
Also in your post you mention that since there are only 3 buff types, you can only have 3 buffs on you at any time. Does this mean if someone casts a +AC spell on you and someone else casts a +Saves spell on you don't get both?
Some nuances, but I really like this idea. Have you posted this on the paizo forums? Last I was there everyone was talking about their own ideas and ignoring everyone else.