I'm absolutely on board with this too.
Surely it's a tiny thing and I am only one player, buuuut when I play any game like this I like to use a hair growth as a marker of time. Is my Tav's hair getting longer between Act1 and Act3? Yep! Would it be nice to see my companions change as well? Hell yep! Maybe someone got a haircut when we got to the city. Who knows?
The thing is, we are gonna be playing this game for years to come (I'm looking at you Skyrim) and while the modding scene is thriving and robust--it's nice when you don't have to RELY on mods for small tweaks and features missing from the base game.
(we should also have far more face, hairstyle, make up, piercing, and tattoo choices but well *ahem* that's a different topic all together *grin*)
