He has four distinct disadvantages when compared with Matt G.
1. He is hurt.
2. He doesn't know the play book.
3. He will cost cap space.
4. He will cost at least one draft pick.
Rather than listing the reasons a QB with 113 starts, 150 TDs / 78 INTs is better than some undrafted free agent from Idaho that clears waivers without even getting a stiff... rather than all that, I will stick to your points.
1. I concede, if he is really injured then the gig is up.
2. Jimmy Johnson was on WEEI today, he said one year they picked up Bernie Kosar after 10 days he came into a playoff game for an injured Aikman and beat SF. The 'they don't know the playbook' thing is overrated for veterans, for unproven rookies it is a big deal for seasoned vets it is not that huge. Fahhh Fahhh Fahhrve seems to have picked up the Jests, plus he added his own ridiculous no look hail mary hook-shot into the mix.
3. Cap - What cap? When was the last time a team had cap trouble? The Redskins have spent like drunken asian blackjack players and always seem to have money. I think they could make the cap work.
4. Draft picks? Fans love their draft picks, remember the uproar when the traded a 2nd rounder for Welker? Man, what a dumb move that was. The team is stocked for next year a 1, two 2s, two 3s. Here is some recent 2nd round picks, some how I think a quality QB is worth more than all of them together. Chad Jackson, Bethel Johnson, Marquise Hill, Adrian Klemm. Yes, yes, there were some good ones Branch, Light, etc. but they don't help my case.
As a side note Garcia is the funniest interview I have ever heard, he talks like he is a cast member of Queer Eye for the Straight Guy. The press conferences alone would be awesome.