so basically, just to conclude this, it seems its just not possible to use vertex lit materials and vertex lights and lightmaps all at once in unity. Unless you have the know how to make some bespoke vertex lit lightmap shader that accepts vertex lighting?
You shouldnt need to use texture memory on alpha foliage. Vertex Color should have plenty of lighting information. Unless you want it dynamically lit from point lights. Set the Lightmap density to '0' on the grass meshes, which will default to vertex lit.
I like it! The only thing that popped out at me is the top room on the corner has 1 window lit but the one on the other side is dark. Both should be dark or lit if its the same room me thinks. Otherwise very cool. Keep it up! :thumbup: