This past season has proven that this team needs depth in the trenches, and a valid pass rush. When you have a starting left guard playing left tackle, then center, then back to left guard so the right guard can cover the center position then the team has depth issues. When the team has absolutely NO pass rush then its an issue. Take the Redskins game as an example. First time Shanahan was shut out, and the Bills had 9 sacks. Fitz looked great! The D looked great!
My opinion, draft pass rusher, or best lineman available (Offense or Defense). If the defense can stop the opposing offense it would take a lot of pressure off of Fitz. Chan wouldn't feel the need to pass all of the time, and he could better utilize Fred and CJ with the run/screen game. Solidify the line and this team becomes a strong contender, immediately. If my name were Buddy Nix I would do the same thing in the 2012 draft that I did int he 2011 draft, minus the running back (Johnny White) pick.
I've also said that the Bills need draft picks that cans start right away. They need immediate contributors.