I would argue that Hall+Ortiz is at least equal to Mayo alone. I think Hall gets a "prospect-boost," for being left-handed, and Ortiz for being a true plus shortstop. Within the game, those guys can be hard to find. Now, obviously, Hall hasn't looked the part at the big league level yet, so, I can understand why people are down on him. Also, I just have a prejudice against minor league sluggers that don't have a consistently strong batting average, so I'm not a big Mayo guy. Just my opinions.
I think this thread and future threads in this forum will be pretty quiet this upcoming off-season. There simply isn't a lot the Brewers will be doing after they make their 40-man/rule 5 decisions. Sure, the corner-infield spots will need resolution, and there will be tinkering at the bottom of the roster, but there isn't a lot of intrigue other than Devin's return package. They'll need a backup catcher, and I'm sure they'll sign a couple of starting pitchers.
Perhaps they could package Devin and Wilken or Boeve for a young infielder with some experience... Josh Smith, Jordan Westburg, Jake Burger, Jose Miranda, or Mark Vientos all have varying success on teams that may either be motivated by Devin or by prospects.