Yeah but you also risk alienating the fans by taking a Doctor many had taken to their hearts (in audio format) and then turning him into a monster.
"How dare Moffat ruin the 8th doctor blah blah blah..."
Yeah, that's the way I look at it.
I was saddened when I heard that Eccleston wouldn't be back (but that was his choice, not Moffat's) and then I was puzzled and annoyed when I heard that they weren't using McGann instead. But it does seem quite clear that there is a reason for using the Hurt Doctor as oppose to any other from 1-8, that he has a role and a function that they can't serve. And this guilty secret, whatever it is, is the reason.
I think it's a safe bet that had we suddenly discovered that McGann's Doctor had done something terrible and forfeited the name 'Doctor', there would be apoplexy among a lot of fandom, even those who haven't enjoyed the audio dramas involving that character and actor.