I don't know how you've fixed it, but in case somebody stumbles across a similar issue, the easiest way IMO would be to copy the original .vmt, replace the VertexLitGeneric shader with the LightmappedGeneric:
then mass-replace the old material with this new custom one and ship it with the map. That way you don't need to search for a replacement texture but you also don't really increase the final .bsp size, because you don't ship any extra .vtf files, and a custom .vmt is <1KB.
Again, nice map overall, such a soft and smooth palette. Would definitely run this instead of churches if I had a gungame server :)