Schaub was moved this offseason because IMHO he was a poor match for the offensive system that Petrino runs. As such, the time to move him was before the draft so that they could get the most for him.
As for C-Pep, if he is willing to play for a small amount it may be worth the investment, but I doubt that Atlanta will bring in such a big profile name before the trial -- even if the "name" can't play for a year.
This is a business. If Vick is acquitted, the Falcons may decide to keep him. They may also decide to trade him, and if that is the case, then they don't want it to look like they are willing to dump him for anything. If he is convicted, well they still have to get a QB and they will draft one next year or dabble in free agency.
I think the Falcons go with Harrington, the Georgia QB that they drafted last year, Redman, and a few other almosts or has beens. A former Louisville QB may also be a possibility (Ragone) or a trade for a JAX QB (or pick up on the WW) if C-Pep signs in JAX may also be possibities.
I suspect C-Pep will also want to go to a system where he is not rushed to play and one in which he is familiar or has familiar coaches. That means St. Louis or JAX.
As for the topic of the post, Brooks would be an adequate #2, but as other posters have said it won't happen. First, the Falcons wouldn't want to jump into that public relations fiasco of signing Vick's cousin. And, second, despite the cash, I don't think Brooks would want to go in to Atlanta at this point since his cousin is still the starter.