I think the banks won't care that much if the government liquidates their preferreds, the banks already have the cash in hand. They don't have put options in them, they would have to sell on the secondary market, which they are allowed to do. It would soak up market demand for any new preferreds the banks might want to issue, but in the short term I doubt that would matter b/c the banks can't issue that stuff at reasonable prices now anyway. And taxpayers would take a bath on those things - bought them at par and would have to sell cheap.
Stimulus will fail to stimulate the economy. It will make effect in 16 to 24 months from now. It does not aim at the real problem "housing market". Doom to failure.