Well the OP's focus is on 1st round and/or 1st picks in the draft and their ability to..well... I'll just quote it:
So Byrd being a 2nd rounder and 3rd selection by the Bills in the draft wouldn't fit either.
Going back to the OP it seems like we're defining impact player as a player "able to make an impact or contribute right away." Moulds was considered by some to be a bust until he finally broke out in his third year. Over his first 2 seasons he only started 13 games and caught 49 passes and 2 TDs.
Based on the definition alone Lynch is probably the closest since he was a 1000 yard rusher as a rookie.
Sullivan loses credibility when he says giving Fitzpatrick the job would be acceptable. Fitzpatrick is awful. I'd rather have Hamdan as the starter next year than Fitzpatrick.
Kelly has endorsed every QB the Bills have had since himself. He probably even liked Hobert. I don't care what Jim Kelly thinks. I kind of wish all the "glory years" Bills would just go away -- aside from Darryl Talley and his drunken tweets during games, that is.
McNair went to the Ravens when he was the same age as McNabb for a 4th. Giving up a 1st, even if you're only moving back 15 spots in the 1st round, would be completely unacceptable.