1.Good idea. This will probably make people buy more hair colours and barber sets, which is a good thing.
2.This is kinda the same as the current situation.(when a rogue is not targeted for x seconds he gets to go invisible).But yes, there should be a small rogue-only damage bonus that rogues get while already fighting an enemy.
3.Nope!If spheres that improve stats other than attack or defence are added, runes and crystals will probably get removed. But the devs won't even think about this, they will definitely say no.