Ok, so I've had an idea. Some may have not noticed, but all the expansion lifestates in TS3 (mummy and vampire) add more days to a sim's life (or live longer than sims, for the simbot matter). What if, in another expansion, it's new lifestate makes the sim live shorter, instead?
So far, the "longer life" has been balanced with the disadvantages of each lifestate, be it walking really slow, not being able to touch water, or not walking in the sun. If a "shorter life" was to happen, the balance would be the opposite; The lifestate would need to have more benefits than drawbacks. Perhaps something that enshortens the life time a sim has every time they use such power - wizardry comes to my mind almost instantly, something like "draining life energy to use the spell".
This whole thing doesn't mean the sim has to die by using the power, as they could maybe age faster (teen, young adult, adult) and lose the power when they become elders, living as long as normal sims after that. Or they could get somewhat stronger when they become elders, but risk dying with every use of their power. I must think of a new ghost color for this too. Maybe later.
Furthermore, wizardry may not be the only lifestate that this could be applied on. Anyone got any ideas?