I would just hate for the new guy to have to mimic too much of 11's mannerisms and wardrobe and such just because writers may have written those stories for 11 not 12.
Sometimes, that actually does a good job of highlighting the distinctions between Doctors. I can think of at least 2 stories where Peter Davison played the role originally written for Tom Baker-- "Kinda" & "The Five Doctors." In both cases, there are instances of dialogue that, on the surface, sounds very Tom Baker but Davison delivers them in very much his own way. Lines that Baker would have thrown away, Davison delivers with earnest sincerity.