I export some mesh objects from Rhino as FBX and reimport it. The objects are on the original layers. Also last I got a FBX model from a client, there was a layer structure implement - very useful.

Layer are quite important for rendering - my clients are using it for sorting materials but also for easy allow to switch between design versions, for example an airplane seat with table in and out.

Attached a FBX in ASCII format there you can see the used layer properties. Only the layer colors are not set yet.

I hope it can be implement. Funny, this way was open since years, but I ask you for OBJ/3dm and layer only always. I didn't know that FBX is so powerful. It seems to be that it can save NURBS too, Rhino ask for it during export.