I think MM will have a fairly big voice in deciding the quarterback he wants running his system. By all accounts, the offense has been put into his hands. I wouldn't put too much stock into his comments about Joey Harrington after he was already drafted by Detroit.
In terms of Idzik's thoughts, nobody really knows, but I lean toward Sanchez not being in the long term plans. If that's the case, Idzik will be better off taking the full cap hit on Sanchez this year and giving himself as much room and flexibility as possible to build the roster next year.