I think the only downside of this approach is the difficulty of getting Stroman consistent work. If Stroman is healthy, and can go 100 pitches, and pitch effectively, then I think you have to get him in there every 5th start. The real trick is how to determine if he's ready for the rotation, without putting him in the rotation.
It's obviously easier to bump Hutch or Estrada from a veteran-PR perspective than MB, although it seems like MB is the one that might be the one is running out of gas the fastest.
Really tricky situation.