We can change horses if there’s overwhelming pressure to do it and it’s exceptionally well planned.
What we absolutely can’t do is nominate someone else against Biden’s wishes and still have him on the ballot as an independent… that’s how you get folks like Woodrow Wilson.
I, personally, think it’s doubtful that much pressure will materialize, but I’m prepared to be pleasantly surprised.
A mask ban for protesters would also limit our ability to stop a pandemic spreading. Mask bans are a bad idea (especially with creepy af facial recognition around).