I don't know if that has already been mentioned, but i think it would be good idea to...SPOILER WARNING!!! Don't read unless you have finished the game....implement some sort of justification why you cannot join de Aldersberg's side in the final stage of the game.This could be done by introducing a flashback, similar to the previous ones a player have seen so far. To achieve this, devs could use the identity quest, which remains unsolved throughout the game.I imagine that the choices you've made in this quest (e.g. killing/saving Vincent , falling in love with Shani/Triss/none of them, concilliating Vodanoy [or whatever you call them] with humans in act IV etc.), would explain why you cannot just decide out of the blue to change your convictions, betray everything you believe in on the spot, and aid the Grandmaster in his mad crusade.By doing so they could also add another, secret ending available only to those who played the game as real two-faced badasses, where you actually can join the Grandmaster.What do you think? ;D