With UE4 only supporting FBX model imports, I think it would be a good idea if the engine were to extend/replace it with Assimp. It has what looks to be an MIT license and supports over 40 model formats. I implore Epic to look into this possibility, as I feel it would greatly benefit modelers and developers.
Sorry to necro post, but I was in the neighborhood.
I found this GitHub - LaP0573/ue4-fbx-importer
Sorry for being gravedigger but i found out about this C++ library and wanted to suggest same to Epic so maybe they could drop restrictive FBX sdk if Autodesk wont release FBX full code in future and relax restrictions of course.
What about code quality if that is acceptable to Epic i dont know.