I think, at least for me, that from a troubleshooting standpoint, Keenum is the last, easiest, most obvious piece to swap out. At least for now. Over the last several years we've had a few coordinators, lots of o line attempts, a decent run game, lots of different guys at wr. What we've never changed is having a backup level guy at qb. When Bradford was here, uninjured, etc, he did ok. He was serviceable. Maybe more. Not really the point. Other than sub par qb play, we've swapped out everything. If you're trying to fix a computer problem or a car, or anything else, you slowly swap out one piece at a time until you fix things.
That's how I see it anyway. We've basically changed everything but the qb, because Keenum, Hill, Davis, and whoever are all basically the same guy. Career backup, known quantity. Injured Bradford basically plays at that level. Keith null and Kyle Boller were that guy. It's the only thing we haven't tried to make a change to.
Otherwise, I totally get what you're saying. I just feel that logically, getting someone in there who we could assume (or at least guess) isn't the problem, would allow us to troubleshoot the offense better.