(Not sure if this would be necro-posting as I'm actually answering that request, sorry if it is x.x)
I could have my try on doing those, I happen to know the map you're referring to and honestly, it's sad it seems to have been discontinued x.x However, to avoid lag I would have to separate them in smaller maps (One 'map' for the ruins, another for Snowdin, etc). My knowledge on making/converting meshes is limited, though, so I might need help to create or find objects for it.