If I remember correctly, you can export a team from a franchise. And in unranked games, I think (not 100% sure) that you can load an exported team. So if everyone who plays the Pats makes a franchise with their team and makes the trades that they made, they will be able to load that team when they play the Pats, and also avoid any unwanted roster updates. Someone would have to test this to make sure you can load a franchise team, but I know that you CAN export a team from franchise...
So if anyone wants to go into an unranked game and try to load a team from franchise, go ahead. I'll try it as soon as I can. Post here with results.