I just discovered iD-indoor, a friendly JS editor for mapping the Interior. It’s been in development for a few years now. OpenLevelUp is a corresponding renderer that renders vector building objects on top of carto. The idea is that, in both the editor and the viewer, features are filtered by level tags. This and similar editors/viewers can map features that share a boundary with a wall such as doors, rooms, corridors, and unwalled areas.

There are multiple ways that OSM could render a building differently. We can remove the roof, exposing the top level at the highest zoom layer. We can use the scroll wheel to cycle through the layers or we can blur relevant features from all layers. Take a look at this interactive campus map. It basically does the same thing as OpenLevelUp. It shows what can be done, as with Zillow, Google, and other GIS organizations.

Maybe iD-indoor should be considered an editor option here on OSM? Edit > Edit with iD-indoor (in-browser editor) or be merged with upstream iD. Advanced features can be made available to users by enabling interior-only and exterior-only editing options.