Yes, interesting topic.
Collison might be an improvement offensively, but here is the thing about Baby. In spite of being pretty short, he has such a prodigious center of mass that is fairly low to the ground, that he's virtually unmovable when he really sets himself.
He is suprisingly quite effective against the true giant big men. Very much less effective against the real mobile centers, where Powe might be more useful. I think Collison could give you some of what Powe does in that respect, but Collison could not guard the big centers that Baby does.
I honestly believe that if we get rid of Baby, we need another center that can guard large centers. It's my feeling that Baby plays primarily backup 5, while Leon plays mainly backup 4.
Again, I think Collison gives you more of what Powe gives you, so, if for some reason you think Collison would be an upgrade over Leon, then maybe swap out Leon for him.
I think Baby's defense against big centers is a little undervalued.
Anyway, I don't know what a proposed package to get Collison would be, but I wouldn't get rid of Baby for him. We'd be worse at backup C if we did. Collison can't guard the Z's and Dwights of the world (and it's tough for Baby, or anybody else for that matter), but like I said, Baby's huge, low to the ground, center of mass does surprising well against those huge guys.
I can't really tell what the proposed deal is. Is the question, would you rather have Baby or Collison? I guess my answer is, for us, Baby, because he plays the 5 better than Collison could against big centers.