Please please please, I would use this feature as an addition to my roleplay, changing hair and look to suit the choices I make for my character.
I also really wish there was a full transmog feature! It's weird to have druids looking like warriors, etc. and I'm honestly really disappointed that nothing more was implemented.
The dye system is pretty weak as well, and mechanically awkward to have to combine with every single item you want dyed. What about combining it with the transmog system and unlocking dyes for future use?