The more I think about it, the more I'm in favor of this line of thinking. For the low minors.
Instead of a starter not making it, and turning him into a reliever. Start them all as short 2-3 inning guys. Then find out who can make the next step up. Actually, start them as 1-2 inning guys in A. 1-3 inning guys in A+. 1-4 inning guys in AA. 1-5 inning guys in AAA.