This will never happen.
It' neither, it just has been happened by posting through the team that this will never happen. The only thing coming close to this is, well, some certain "customisation".
I understand that you meant additional setting that allows one set if he can be easily recognized or not? That may do. It could be done by a command '~addfactioninfo'.In case of NPCs faction i would suggest no exceptions since killing one of the npc faction players affects reputation so it's essential to know what faction player is in.
Nope, "Bodypainting" is the keyword.