after reading this I am sorta torn
for one thing I think it would be awesome to play as a phyco, snapping and killing everyone on sight, just becoming a sort of monster, the gameplay would change greatly and it can turn into 'how long can I survive like this' mentality and can be fun.
BUT
I also think it would be terrifying, but also awesome to have control of your character be taken away, and you watch the character you've done so much with, built up to be this awesome person completely ruining everything, the control is out of your hand. You can't do nothing BUT watch such a scene, but it would not end there. Like having your character possibly screaming in rage and pain, maybe hearing the insane thoughts of your character, things start to change and look more and more screwed up. You can't even pause the game to reload where your character was sane, all you can do is just WAIT until you're character is taken, gundown, or snap out of it. It can really have an effect on the player to realize to have a real good 'oh shit' moment of silence.
I think we live in an age in gaming, when it comes to the 'choices' you make it comes down to squat, and no matter the choices we make in the game the character will usually always come out on top. I think that it would be nice to have that feeling of powerlessness because you, the PLAYER decided to get too greedy and put too much stuff in your own character and it was truly YOU who screwed up. Not the game. I think that would be a real good change of pace from todays games and I would like it, I would hate it at the time it happens, but I would like it.