I have not tried the plugin, but have a quick question:

What gets added to the associatedStreet relation? The interpolation way, or the addr:housenumber nodes therein?

But: bloody brilliant! I just mentioned needing something like this in JOSM to a few ppl on #osm-nl, and look what you cooked up! Great! :slight_smile:

PS: We would also need a way to add further addr:housenumber nodes (that are inserted into the interpolation way) to the appropriate relation as well.