You could put disused: prefix in front of amenity= and optionally delete other biz-specific tags.

If you haven't already, check out app called EveryDoor. It's on both, Android and iOS. It's designed specifically for editing POIs features with easy presents for a lot of things and it has a single button way to mark biz as closed.
You can't create ways with it like with Vespucci, but for POIs it's a lot less clunky. 🙂