Guess the 46 is the best way to go about this. The last 7 are basically a developmental stash for redshirted players that are too risky to expose to the PS. And don't forget the needs of the STs.
My early guess for the 46, assuming Tank not suiting in the early part of the season, Lattimore in IR/PUP, Manningham available health-wise and no major surprises in TC (there are always surprises, but by definition you can't predict them
Kicking team: the three usual suspects
OL (7): Boone, Iupati, Looney, Staley, Davis, Snyder, Kilgore. I think Goodwin is a cap casualty unless he takes a pay cut.
QB (3): CK, McCoy, Daniels if he can help in ST, otherwise Tolzien and Daniels to the PS.
RB (5/4): Gire, Hunter, LMJ, Miller, [Dixon (ST)]
TE (3): VD, McDonald, Celek
WR (4/5): Crabtree, Boldin, Williams (ST), Jenkins/Manningham (if Manningham doesn't beat Jenkins by a big margin I see him cut), [Moore (ST)].
Re: Dixon/Moore. I can see us carrying 4 RBs and 5 WR if the 5th receiver is more of a help in STs. If someone like that emerges, then it's curtains for Dixon.
DL (5/4): Dorsey, Justin, RayMac, Ian (if he can't get in the 46 regularly this year he's not worth keeping) [+ 1 more from the rest depending on scheme]. I can see Dial in the 53 but not suiting up and one of the Dobbs/Tukuafu brigade suiting up instead, but that really will depend on the camp showings.
LB (7/8): Aldon, Brooks, Haralson, [Lemonier], Willis, Bowman, Moody (primarily ST), Skuta (ST). If Haralson gets beat in TC by Lemonier he could be in trouble. Alternatively we can carry both and keep 4 linemen.
DB (9): Rogers, Brown, Cully, Nnamdi (I assume he shows enough in TC), Spillman (ST), Whitner, Reid, Dahl. There needs to be one more STeamer here (eg. McBath or Brock) and that's a TC battle. My early money is on Brock. I don't see Cox making it unless he lights it up in TC, in which case it would be the end for Nnamdi probably.
That makes it 6 or 7 ST specialists (+3 in the kicking team). Predicting the ST squad particularly after last year's poor showing is tough at this stage.
The 7 man stash is just made for people like Tank, Dial, Patton, Lemonier (if he gets beat by Haralson), a couple of DBs drafted in the last couple of years, and the odd crazy prospect that is not safe to expose to the PS (e.g. Okoye if he pans out). Plus of course room for non-IR injuries