I measured out my Japanese build, and it can easily fit inside a quarter of a sim, or an eighth without the pond and dock (or maybe even with, if slightly modified). Also, I had moved the house from another sim previously so most of it has already been grouped into multiple objects.
My plan is to take each object and verify owner and perms for all assets, including textures and scripts, making sure I have rights and ownership to everything in preparation to the move to a sim in Kitely which Fauve Aeon has generously offered. Only a few textures are from someone else in isolated spots so it should be relatively easy - I'll just need to replicate them (in spirit - not illegally).
In addition to the move, I will also make full perm copies of the mansion, pond, dock, and teahouse available free to the community, so the build never gets lost even if/when I leave SL. I've got a month to do this, which is workable. It stands up well for a 2010 build, but it really needs some updating.