Belichik took a crappy Cleveland team to the playoffs in his first HC gig.Like has been mentioned, Belichick is a coach that got better on his 2nd time around. It's not uncommon, especially for a guy who got his 1st job in his 30s, to do much better in his 2nd shot at HC. There have been plenty of guys that have gotten 2nd jobs pretty much right away and had more success (Reid, Coughlin), but in particular, guys that wait a few years before taking their 2nd job (Belichick, Carroll) really tend to do well the 2nd time around. McDaniels is as much of an offensive genius as there is in the league right now. I think he probably can better deal with players this time around.
That being said, I think he's waiting for Bill to retire and just take over that position. But McDaniels is a guy that would probably have to be given significant roster control and probably would bring in some familiar faces from NE to surround himself with. Bears would basically have to be New England West in the way that it runs, which probably aint happening.