I will respond to both of you here, since there are similar things said. The performance aspect (Rochester being a bad team) isn't necessarily improved with these has-beens rather than prospects, and there might be more appeal for minor league teams to have prospects that people want to come out and see (any word on Beloit's attendance this year, for instance?). One thing I thought was an improvement over last year is that the Twins initially signed AAA player that were actually pretty good (Burroughs, Carson, Ramirez, Florimon, etc.) as opposed to the Chase Lambin and Jeff Bailey type. Thurston seems like the latter variety, but oh well.
Revere is Exhibit A! I don't mean to say that they Twins should promote fast to MLB, but rather to get players at the highest level of MiLB and see how they perform. This means that I like in-season promotions (for many reasons, one of which is if they are going to move up a level at the beginning of next year anyway, it's good to prevent slow starts by having them be familiar with the next level already--see Aaron Hicks 2011, Michael Gonzalez this year, etc.) and I would have just liked Rochester to have a team of Revere, Benson, Tosoni, Parmelee, etc. last year for some period of time together. Now they are all over the place (Parm 2/3 time with the Twins, Revere up and down, Benson and Tosoni struggling (I know Tosoni is hurt, but keeping in mind last year) at AAA, etc.
The general idea is that I like the team to stay in-house first, giving guys the opportunity to perform when they are already here as opposed to adding Clete Thomas, JR Towles, Joe Thurston, etc. Good lord, is Clete Thomas (aside from being a lefty) really going to be better than Matt Carson for the Twins? JR Towles rather than Danny Lehmann? Thurston rather than Florimon or increased time for Chang?
Meanwhile, instead of AAA has-beens, why not find more Chris Colabellos to start at AA or lower and see what happens. Or under 25 guys who still might develop, but could use time at AA or A+ while promoting guys there up a level?
I don't know the details of the Baseball Prospectus study about minor league service time. The 200 PA more than everyone else doesn't bother me as much if the stagnation occurs at higher levels in the system (and it just happens that players end up not being very good), but I get the sense that a lot of it happens a A/A+.