If Redman goes to the PS, he's gone, a team will look at film and bring him in for depth at RB. Trying to hide him there will be a mistake in my opinion. Summers, may or may not, clear the PS, but the Steelers can't protect both.
I don't see Parker and Mendenhall both getting through the season unscathed, neither has proven that they can do that in recent history. The Steelers are going to need another RB this year and Logan isn't him (WR maybe, not an RB).
Keeping 10 secondary players seems like a luxury, but maybe not. Of course, if any of the 10 listed in the first post go to PS chances are real good they get picked up by another team. I thi9nk I would let Ratliff go and keep Redman or Summers on the 53; the Steelers have players that can play safety if needed. This would also put Logan as a WR where he belongs.
The Steelers are going to have to expose a good football player to other teams or not put Logan on the roster (unlikely at this point) to protect some of their good young talent.
Just my 2 cents...