@Kenmo - why aren't you using Modo with Mesh Fusion for your modeling now if it generates the type of model that you need?

Right now you're trying to use a faulty toolchain basically. You're starting in MoI which has no focus whatsoever (not in modeling nor in export conversion) on making all quad edge flow based model structures and then your downstream tool requires only all quad edge flow based model data.

You're setting yourself up for a lot of pain and suffering by trying to force a toolchain together that does not connect together.

You should probably pick which side you spend the most time on (modeling or uv mapping/texturing) and swap out the other side for something that is compatible.

- Michael