I believe the Bills need to get Clay, he will make this offense so versatile, we've never had an option at TE like that.
I like the fact that they aren't trying to move everything in order to bring in a slight upgrade like Bradford or Foles (Bradford too injury prone, Foles seemed to be a beneficiary of the Eagles system, imo). The thing this team needs to do is get a solid group around the QB, whomever it is. Seattle had the same game plan. They had a question at QB, so they traded for a big name back, built a strong defense, and build up the offense around the QB.
Get Clay, sign another offensive guard (Jahri Evans? Steve Wisniewski?), Felton is basically a 6th OL for power running, and in the draft go with Fuchness or Maxx Williams in 2nd round, then get OL 3rd, linebacker 5th, CB/S 6th. Also, sign a NT so Williams and Dareus can play on the ends in this defense, giving Rex more ability to use them to get to QB as well (Dan Williams?).
This is how I would do it if I were then, gain an identity this year, and if in the off-season next year a QB becomes available (Brees is NO rebuilds, Kaepernick if he continues to regress, Cutler or Bradford in FA, or 1st round in 2016 draft), that's when you pounce and your team is ready because the positions around QB at that time will be strong.
My 2015 Bills Depth Chart:
QB: Manuel/Cassel/
RB: McCoy/Jackson/Brown
FB: Felton*/Dixon
WR1: Watkins/Hogan/Goodwin
WR2: Woods/Fuchness*/Easley
TE: Clay/Fuchness*/Chandler
LT: Glenn/*3rd round pick*
LG: Evans*/Urbik
C: Woods/Urbik
RG: Incognito/Richardson
RT: Henderson/Kouandijo
LE: Dareus/Charles
NT: D.Wiliams/Charles
RE: K. Williams/ Bryant
LOLB: M. Williams/Lawson
LILB: P. Brown/*5th round pick*
RILB: Bradham/Powell
ROLB: Hughes/Lawson
CB1: Gilmore/McKelvin/Brooks
CB2: Graham/Robey
FS: A. Williams/ Rambo
SS: D. Williams/ Meeks