The Bills could stand to upgrade at every o-line position. Assuming the medical issues are cleared, YES, sign him. He still has several years of NFL time left, 2nd team All-Pro, even if you have to over-spend, if you are serious about protecting your franchise QB, you sign him! And continue to look for upgrades in FA and the draft.
I would be all for signing him, drafting another tackle in round1 or 2, and moving Dawkins inside . . . do whatever you can, anyway, you can, to upgrade the line.