I'm not a Gaddis fan. I know he only got seven innings in Cleveland last year but he was awful. Small sample, I know, but he'll be 25 in April. Gaddis and Battenfield are ranked as our 37th and 40th best prospects by Fangraphs. There are 13 starting pitchers ranked higher than these guys. I'm not worried if they have to start the season at AA.
That leaves Morris, Pilkington, Williams, Bibee, and Allen at Columbus and Castillo, Espino, Battenfield, Curry, and Gaddis at Akron. I would actually trade Plesac for a prospect, promote Morris, and move Castillo up to Columbus to start the season.
Curry will be 25 this summer and had a 4.38 ERA in Columbus last year in 53 innings. He's a 6'0" right-handed starter and not many of those have successful major league careers. Battenfield is 25 already and struck out 109 in 153 innings at Columbus. In a season where Curry, Gaddis, and Pilkington got called up for spot starts Battenfield did not. I'm not high on Battenfield, Curry, or Gaddis.