I'll give it a go. One nice way is to tag all the businesses as individual addressed nodes in a way that respects the entrance to them, and put them inside either a named building or better still behind a named entrance on entrance=main at the building's edge. The building and/or entrance wouldn't have address parts; instead, the individual unit nodes would.

The 8 nodes inside https://www.openstreetmap.org/way/332467991 is about the closest example I've done. It's certainly good enough for people searching, given that we normally can't get accurate positions of things inside private buildings.