For a former church, I would just use `building=church` and set `old_name` to the most used former name. If the history is notable beyond that I'd [check for a suitable historic value](at https://taginfo.openstreetmap.org/keys/historic#values). value](https://taginfo.openstreetmap.org/keys/historic#values). A pub is harder, tags like `was:amenity=pub` are seeing some usage, and `old_name` would again be reasonable.

For a former church, I would just use `building=church` and set `old_name` to the most used former name. If the history is notable beyond that I'd [check for a suitable historic value](at https://taginfo.openstreetmap.org/keys/historic#values). A pub is harder, tags like `was:amenity=pub` are seeing some usage, and `old_name` would again be reasonable.