If CDM would now start Trask, would it not be an embarrassing admission that he made a terrible mistake at the start of the season?
No.
There could be myriad reasons to roll with Franks first. He does have physical tools that are fantastic. Mullen was clearly bringing Franks along slowly, building his confidence and protecting him and fostering his success through scheme and play design. It seems reasonable to give Franks a chance to prove he can grow with proper development.
It's also true that Franks was executing better earlier in the year than he is now. ...even against good competition. I'm also confident that Mullen does know more about the relative strengths and weaknesses of the QB's. Franks may excel in areas that Trask and Jones don't. I believe Mullen will have all of the advantages and disadvantages of being close to the situation. ...better knowledge of what's really going on (especially in light of plays called and what each QB can do with them) and being 'too close to the situation.'
I don't think Jones is ready, based mostly on what Mullen said last week about knowing the offense. If you have the base offense down, then only the new installations each week are new to you. If you don't know the base offense, then more of it is new to you and you're at a disadvantage. Certainly some of this is due to Jones not getting second team reps all season and some of it is due to him being a first year player.
As fans, this seems like a much simpler decision than for the people actually leading the team and the QBs. ...and the simple perspective (in sports, politics, relationships, etc.) always makes one feel confident that the solution is easy. Having said that, I would rather Trask start against USCe.