First off, I'd definitely look at trading Franson (he'll have more value than Ranger/Fraser and I think he's hurting this team a lot with his bad defensive play... his offense on the PP isn't making up for it IMO).
Secondly, if we get a good defensive Dman, I don't want to see him with Dion unless we're trying to hold a lead or maybe if we're going against a team like the Caps/TB (who have one very strong offensive line).
Gardiner - Phaneuf
Rielly - Girardi/good defensive Dman (would love somebody who's a #2/3 DFD)
Percy - XXXX (Most likely Gunnarson, possibly Ranger if he continues to improve, possibly Fraser, or Finn?)
This would be a really solid defense that has some physicality (Phaneuf and Girardi), mobility (Gardiner/Rielly), good defense (Phaneuf, Girardi, Percy?), offense (Gardiner, Phaneuf, Rielly), and everybody is at least adequate defensively (depending on which Gardiner shows up... he's had good and bad games defensively so far this year... Rielly's shown that he can be a good TWD, just needs time to figure out defensive positioning when the opposing team is cycling...).
Edit: Who knows, maybe by next year Rielly is able to play top pairing... But having Rielly-Phaneuf (If Rielly reaches potential), Gardiner - Girardi-type dman would be awesome.