I know this is probably beating a dead horse and I may be verbally accosted for writing this, but could this happen?
Could he be a part of the team in a role like Chris Harris? I mean he may not be able to play anymore but he was one of the best at his position when he was healthy. He could help train rooks on the proper technique for the position, help them learn how to read an offense, help them with the nuances of the position.
It would also help to have him there as a show that the team takes care of their own. This would also give Brian a chance to save face with some of the fan base, because he would be coming back to the team "He loves so much", but in a different role where an offer wouldn't be an insult to what he did on the field.
He could finish out his football career in The Greatest Football City in the World and would be able to help mold the next Great Chicago Linebacker. Just my opinion...