I think the correct way to do this is to allow a rollback to the immediately previous working version. Before updating, write current firmware to failsafe data

I think the correct way to do this is to allow a rollback to the immediately previous working version. Before updating, write current firmware to failsafe data storage, then do the update. Then a firmware reset sends you back to the last good version. I'm pretty sure this is already done by many hardware and software manufacturers, such as me.