Why have him back at all then? If you want something radically different they might as well just invent a new character.
Certainly mean less pissed off people who were fans of him as was who'd consider it a con to be served up a changed person.
Because I'd prefer him not to be a cardboard cutout. I don't see this as a radical change, though. He's the same man, and personally I am more interested in seeing what might have caused this shift in him than just see a rehash of him on the Enterprise.
New Trek just can't win. Fans want something new, but they don't want change.