Theoretically, you could use negative feedback loops as a means for elegant balance across disparate systems, in a way that is not fixed but rather mostly self-adjusts for the actual game being played. The trick, of course, in tabletop games is to do that without making it too complicated and/or counter-intuitive.
For a crude illustration, say that we have a mechanic that tracks the amount of magic used by each character over an adventure (or period of time, if you prefer). Assume they are still using traditional Vancian slots, or something similar, for tracking of spells. Then in addition, you have a bonus or penalty to the level of the spell, based on how much has been cast by that character thus far. (You'd need the ability for higher level spells to be cast as if from a lower-level caster.) This adjusts as magic is cast.
So Blastum the wizard sets off with his friends. Since nothing has happened yet, he gets a +3 level to all his spells when figuring the effects. They meet some piddly orcs, and Blastum being that kind of guy, uses a fireball on them, practically ending the encounter. That's a third level slot. This goes on the counter. Maybe that was enough to drop him to +2 level on his remaining spells. Keep it up, he can go all the way down to -3. The more he does, the less effective he is. (You can rationalize this as fatigue or any number of such things.)
Ideally, you then give your standard wizard more slots than he should normally use. Now, he also has a bit more flexibility, in that he has spells prepared that he probably won't use if played efficiently. Because there is some optimum point at which he becomes increasingly ineffective. We don't know exactly where that is, but it doesn't matter. It's there. It being there is what harnesses the power gamer instinct into restraint.
Finally, there are tweaks for each group, which is what makes this really work. If Blastum is really feeling frustated and not accomplishing much, up the range and/or up the threshold. Now he can do more. OTOH, if everyone is ticked that Blastum is dominating every encounter (or Blastum's player is embarassed that he is), lower one or both. Now he has to be more strategic.
Now obviously this is a variation on the conceit that magic is relatively rare and powerful and should be conserved carefully for when it matters. Depending upon how much you valued that conceit, you might also tinker with the numbers in ways that had nothing to do with balance for other characters. (That is, the wizard might be thus tweaked into a dominating character or shoved back into a supporting sage, depending on your inclinations.) Even then, though, there are still concrete, flavorful limits.