As for the Boren defection. No matter what you hear in buckeye land, Boren left because he was being singled out by Barwis (michigans strength coach) for being soft and not working as hard as everybody else. Boren was a prima dona that couldn't hack it when he was forced to take his training in a different direction, and with a level of commitment that he had never had to go to before. Bottom line. End of story. As for who was right? I'll take Barwis on this one... Quick did you know... Leading up to the 2008 NFL season Lamar Woodley opted to train at Michigan with Barwis instead of working out with his fellow Steelers. When starting his training regimine Barwis asked Woodley to set his goals. Woodley set them, and Barwis laughed, then gave him new tougher goals. Woodley said at the time he thought Barwis was insane, but within 2-3 weeks Woodley was able to meet each of the lifting and sprinting goals that Barwis had created for him... Led to a pretty decent 2008 NFL campaign iirc.
Finally, Rodriguez HAS had success running the spread without a terribly mobile QB, albeit one with a bit more size. In 1998 he led Tulane to a 12-0 season with Shaun King as his starting QB. King wasn't the most mobile QB in the world, but had 156 carries for 633 yards at 4.1 ypc. However he was 244/364 with 3495 yards passing and 38 TD's. That offense wasn't the same one as the one he ran at WVU, but he adapted it to fit his personnel, and it worked well.
Either way... The correct QB will be there next season when Devin Gardner comes in. He'll also be an early enrollee, so it will be interesting to see how that works out. 6'4"/195, good (but not dynamic) runner (though rivals does rate him as the top scrambler) with the 2nd strongest arm in the country.