Wow, what an awful thing for Moffat to say. My respect for him just declined precipitously.
I was wondering myself what they would have done if Tom Baker wasn't available. Peter Davison would have been just fine with me, since he's "my" Doctor. But any of the Doctors would have been fine with me. Maybe they would have put David Tennant in old age makeup.
Well that quote was from 20 years ago, and from the sounds of it alcohol had been imbied, and whilst I probably wouldn't have put it quite so harshly, he does have a point with regard to acting ability.
If Tom Baker had proved unavailable, I think David Bradley would've been a good choice... He'd have supped for Hartnell, as per the Adventures in Space and Time.
If anything, it'd been a nice nod back to that's ending.
I guess it depends which came first, the role of the curator or the availability of Tom. Did Moffat always intend there to be a curator, or was the role created once it became apparent Tom was willing to appear. If itís the former then Peter would have been the logical choice (and there would have been an interesting synchronicity, the two youngest Doctors meeting) but if itís the latter then the scene might have played out very differently. Other than with Tom or Peter I canít see that scene as working very well.