Michael, couldn't you not allow to write meshes to 3dm files please, please .... . Anything could be so easy, since MoI got "layers". The 3dm format allow to contain meshes and NURBS, it could be a great help. Maybe you can build in a hidden door for that usage, for example that mesh export to 3dm works per script only. Than I could export my geometry from Rhino, open it per script and save it as 3dm. No UI change would be needed. It's some extra work for you, but I suppose so it will cause some extra MoI user too. ;)
Rhino v5 will not have a better mesher and I need Rhino for rendering with Vray. So, MoI is my escape for complex models. An easier workflow would be great for all render users like me.

For now - replacing spaces isn't a good option. The workflow will be more difficult. I wished, the mesh grouping/joining could be avoided. I afraid it cause problems and I never missed this feature.