What I would love to see is some form of dynamic hair growth for the PC. In The Witcher 3 you saw Geralt’s beard grow from clean shaven to a bit of a five o’clock shadow (I have to check that as I haven’t played it for a few months and I left him with a beard) to a trimmed beard to a bit scraggily, there were more beard lengths but they were cut to accommodate the free Beard and Hair Style DLC, I do not know if his hair grow before the DLC.
It would be cool to see your character’s hair and beard (or just hair if it’s a woman) grow. Now there would have to be some limits not everyone can grow a ZZ Top but it would be good to start off with a clean cut character and by the end of the game he looks like Grizzly Adams.