OK, I started this tongue in cheek but you're obviously thinking seriously. I'll try it your way.
Why would he leave the team he has played for his whole career? Because they suck, and will suck for the foreseeable future. I would think he would just retire rather than tarnish all he's accomplished but he has said publically that he wants to play more.
So where would he go where there is a better situation? Hmmmmm what team is on it's way up but just needs an old QB? Actually, I can't really think of one. The point is, anywhere he might go where he could start would probably be as bad or worse than GB.
If Jerry sold hard, he could paint a pretty good picture. C'mon down here, close to home and have some fun with us. This kid Romo just loves you and wouldn't it be great to put the exclamation point on your career by helping this kid hit the big time. Hell, the way he runs around, there's a decent chance he'll get his bell rung anyway so we'll probably need you to play a little bit. Let me throw a couple of million your way just for incidentals cause we're not paying him much. Besides, I like your style and I could introduce you to some of my lady friends around here. C'mon down Brett and get yourself another one of those big'ol super bowl rings.