You're just writing this because it's the boring part of the off-season, aren't you?!
The grass is always greener on the other side of the fence, until you cross over it.
The other lane is always going faster, until you get in it.
The other player always looks better, until you sign him.
Yes, I think Tim Rattay would be a decent back-up somewhere, but exchanging him for Collins is going to have marginal impact on the team -- unless they get into a game. Then, it will probably be worse in either case.
I'd rather see what we have in Hollenbach and Palmer and move one of them up the depth chart.