What is unreasonable, is giving up top prospects to obtain the right to negotiate that deal with him. Boston's offer of Crisp and Lester plus some C prospects is laughable, particularly when compared to the Yankees package -- even before the inclusion of Hughes. In Minnesota's current state -- the first phase of rebuilding -- Crisp would be a payroll liability. His production last year was roughly equivalent to Melky's, and though his secondary statistics point to better performance next year, he's already in his prime, and must be paid $5 million this year and next. Melky is years away from arbitration, and years away from his prime. For a rebuilding team, the most important difference is the $4 mil saved (on avg) over the next two years.
I'm running out of gumption, so a little gloss here: Kennedy is expected to be better than Lester by most prospect ratings, has an extra year before arbitration (read: cheaper), oh, and doesn't have CANCER. The rest of the prospects mentioned by the rumor mill aren't so highly touted, but Tabata (18 yr old Yankee CF) has by far the highest ceiling. He has Tim Raines like speed, and with his smallish frame, may never develop much power, but he makes good contact and could be an above average leadoff type if he can learn to take some walks.
My point so far, is that Hughes doesn't need to be included, the yankees have already put the best offer on the table. The twins' only motivations for keeping santana another year are the tickets he'll help sell this year, the loyalty of fans lost by winning less games this year (future ticket sales), and the compensatory first round pick they would receive if he leaves as a Type A free agent. They shouldn't give him away for nothing -- those concessions are worth more than the $13 mil he'd be paid, but between Melky and Kennedy, the savings they'd keep make this a winning proposition.
For the Yankees, including Hughes would be worse than waiting a year and paying full free agent price for Johan's services. This could probably be closer to 28 or 29 million per year. Since Hughes is years away from arbitration, and expected to be an above league average pitcher, the economics of the deal should include this lost value. The market difference is larger than that the difference between the two scenarios for acquiring santana now vs later.
Hughes, even alone, in a 1 for 1 deal, should not be traded for Johan -- as long as the alternative is that Johan goes to free agency next season. As long as the yanks are providing the best offer sans Hughes, including him shouldn't be considered. Cashman knows this... does Hank Steinbrenner?