I'd be more inclined to overpay for Johnson the Halladay. Johnson is coming into his prime. He might be further along then when the team acquired Beckett. Johnson you have I think for at least 3+ seasons with no extension. That's someone that is worth putting Buchholz in a deal for.
I know Johnson and Hanley are the faces there for the Marlins. But Buchholz, Bowden, Anderson, OF prospect + other prospects from a trade of Bay(you would think he would get something decent) and whomever else, is a hell of a package to fill out your ball club for some time to come. And all would be ready to debut for the opening of the stadium possibly. Add that to Florida's already strong young core and they could be legit for a long time.
This is all speculation though. Just kicking around names outside of Doc and V-Mart.