@ Wishgrater,
I saw your demo using unity, nice preview but i see that your also having issues using high res textures with unity.
Im having the same problems, i need to import a large model, half a city, into unity. No problems on the mesh side of unity, it runs perfectly even with 2 milj polys, but i can only use one 4k texture.
A possible solution could be to cut the mesh and calculate a new texture using Photoscan but this would require very preciece cutting that is not doable in PS. Any ideas?
best,
Mike