Sorry, I misread your suggestion. I thought you were suggesting a CRL-like behavior. If you're just talking about adding an SSH-like warning, and not manipulating or revoking the certificates on the browser itself, then I take back what I said.
Of course, the SSH warning has been shown to be fairly ineffective in the real world. And that's with sysadmins who should know better! What about regular people? When presented a dialog box saying "The certificate for Chase Bailout Bank has changed! Do you want to continue?" I would guess that 99 out of 100 of them would simply click "Yes."