I think that as a whole, MLB's umpiring could be improved with the firing of about 10 guys. It seems like the same guys blowing calls over and over. On the flip side, there is probably 10 or so exceptionally good umpires in MLB. The rest are just meh.
I don't know how much it would cost if the league had to buy these guys out, but it would be money well spent. Earlier this season the Jays had a game with a 27 year old plate umpire. I don't remember his name, but he was very good for the 7 or so innings I watched, so the talent is out there to improve the crews.