If Burnes, Woodruff, Peralta, Lauer, Miley, Ashby, and Houser are all healthy, there won't be many starts available for the 7th guy, even if they use 5 days off for everyone. When I scheduled out the first 41 games, those guys got 8,8,7,7,5,5, and 1 starts, respectively.
The thing is, them being all healthy, even for only the first 41 games, is very unlikely. I don't think jettisoning one of the others for the sake of Miley, who pitched less than 40 innings last year, is wise. Unless we want to parade junk like, well, Junk and Alexander in the rotation.
So, what can they do--until an injury settles the issue for them?
Use whomever is not scheduled to start within the next 5 days as a "first man up" in the pen, with the idea that they'll pitch 2-3 innings. A benefit of this would be to lessen the burden on the back end of the bullpen, of which only Williams should give us much confidence.