If you don't collapse it, but simply export it as a scene with multiple objects, blitz will load it as one mesh (using LoadMesh) with multiple surfaces. Each surface will have the diffuse map on UV channel 0. As far as I know 3DS doesn't support more than one UV set. You could export it twice, one time with the duffuse map and the second time with the normalmap. then import both in Blitz and read out the normalmaps UVs and set them in the other mesh.
Maybe if you use some export paths for the B3D format you can export both sets in one step. (b3D pipeline or something, or the max to dx8 to ultimateunwrap to b3d path). However, when you load a mesh, the order of the surfaces will not be the same every time, so you need to identify each surface by the filenames of the textues used by the brushes (see SaveB3D example in the code archives on how to determine the used textures)
Hope this helps.
Maybe if you use some export paths for the B3D format you can export both sets in one step. (b3D pipeline or something, or the max to dx8 to ultimateunwrap to b3d path). However, when you load a mesh, the order of the surfaces will not be the same every time, so you need to identify each surface by the filenames of the textues used by the brushes (see SaveB3D example in the code archives on how to determine the used textures)
Hope this helps.