Firstly, there is the issue of Brady's age. The guy is coming up to 32 and is recovering from a serious injury, which has been further complicated by infections. Matt Cassel, his highly toted interim replacement, has exceeded all expectations and is five years younger.
Obviously, Cassel cannot hope to match what Brady has achieved in his tenure in the NFL. But look at the stats of Brady's rookie season compared to Cassel this year. Cassel has less interceptions and more touchdown passes.
Of course, Cassel has the advantage of an awesome passing offense and great wide receivers, which Brady didn't have in 2001, but I would even go as far as saying that Cassel was one of the better quarterbacks in the NFL this season.
Although it is obvious that Cassel cannot completely fill the void left by Brady, the benefits that the Patriots would receive if they traded Brady are huge. He still has that aura of invincibility around him, and I have no doubt that other teams would give almost anything to acquire him, including draft picks, young talented rookies, not to mention a large stash of cash.
Brady is paid A LOT and the money that the Patriots save and earn from his sale could be used to usher in some awesome rookies or free agents to sharpen up the defense.
Both the Ravens and the Steelers have showed what a great defense can do for a team's chances of success. If New England used some of those draft picks and extra cash and trades that selling Brady would bring, they could greatly improve their defense, which is by far the team's weakest point.
A great Patriots defense coupled with a Matt Cassel/Moss/Welker offense (and that offensive line, of course) could start a new era of domination!
My last point would be this: Everyone hates Brady, right? Unless you're a Patriots fan, you hate the guy. But I would imagine that if he moved, he would become a fan favorite (no doubt).
New England could easily manage selling him to a team outside of their division so that in the instance that Brady did manage to transform a losing franchise into a winning one, they would not be threatened.
Additional benefits could be worked into the deal, similar to the agreement between the Jets, Packers, and Brett Favre, where if Brady took more than, say, 60 percent of the snaps, the Patriots could get more benefits. Or if Brady leads the team to a division win, the Patriots would get additional benefits.
I know it sounds crazy, but give it a thought!