Altering sims personalities during gameplay

I think that's a really good idea, I'm just not convinced they'd be able to make it nuanced enough to do the execution justice, with it being such a fine balance. I wouldn't want an evil sim becoming good after performing three good actions and vice versa (since you know, even evil sims can have a soft spot for someone/something, and good sims can do mean things in the heat of the moment). But I do like the concept!

The Parenthood character values come to mind, because at least there you can see where your sim is in terms of gaining a particular trait - but that system alone kind of shows how tricky this could get. I put very little effort into parenting my sims' kids and yet somehow they get the good character values just by performing everyday actions, meanwhile, if I want any of the bad ones, the only way I've been able to achieve them was through cheating. So the calibration would have to be done really carefully!