He has to turn ugly. It would be stupid if he only became prettier. At least Jiroubo and Kidoumaru so far seemed to have gained thick skin of sorts... well, I don't know, but he has to look ugly, even if it is bad-ass ugly. Ugly enough that when/if he comes out of the barrel, the others will see him and go "OMFG is that Sasuke?!" and then Naruto can lecture him... or something akin to that.