It is an inspired idea, but I agree that a protest outside of One Arrrowhead (with a tip to the media) would be more effective. To be truely effective, the banner would need to be done during the game and picked up on TV.
If you are going to do a banner, I would delete the point about firing Pioli. That isn't going to happen this year. You turn Pioli against us as well. If you just call for the replacement of Cassel (and maybe RAC), then Pioli can get behind it more easily (as can Clark Hunt). Though Casshole has been seen as Pioli's golden boy, if there is a fan riot, he can use that as an excuse to agree with Hunt to select a QB in the first round next year.
Pioli's failings have been the 2009 draft, as seeing Cassel with ill-founded rose colored glasses. Otherwise, he has drafted fairly well and has done okay with recent free agent signings. His selection of RAC as head coach is understandable. I supported it at the time. Now it is clear that it was a mistake.
Again, Pioli does not get fired this year (regardless of what Babb and Mellinger chant). It is better to focus on getting rid of the most important failing of the organization -- Cassel. The second biggest failing, I hate to say, is Crennel. Focus on the most important and don't dilute the message by spreading the hate too broadly.