So I spent some time over the last few days taking a stab at instantly being able to import 3D models, as opposed to the image placeholder while they process on the server, and... it worked! The 3D placeholder might be in a slightly different position than the processed model, and the colors/materials might be a bit off, but I think it's a great improvement.
I also addressed some outstanding bugs having to do with editing environment attributes (background color, name, etc) with the current environment menu (below).
Previously, sometimes the current environment would become unselected by its menu, so when you'd try to change the color or whatever, it would either do nothing or change some other environment's color. Anyway, that should all work now!