The Bills have an example to follow - the late 1980's team. They get Bruce Smith in the mid 80's and build a solid defense around him, they pick up Kent Hull and Kelly when the USFL blows up, they bring in Polian around the same time and then bring in Levy midway through the 86 season. They build a fantastic offensive line with Ritcher, Ballard, and Wolford some of who were already there. They build the offense around Reed and then get Thurman in '88 and away we go. And by the way, they brought in a superb special teams coach and had a top-tier special teams group.
Kelly was certainly a key piece of the puzzle, but not the only piece. I'm guessing that Allen can be a great QB too, but he can't do it alone.