Support external Bethesda material files (BGSM/BGEM)
Many Fallout 4 and Fallout 76 assets (and eventually, Starfield assets) currently look white because their shader properties and texture sets are supposed to be overridden by external material files which OpenMW can't load. There are various utilities that can load these material files. While this would not necessary be practical, it would be pretty great if we could load these to some extent that can be increased as BSLightingShaderProperty/BSEffectShaderProperty get better support.
The benefit of external material files is that they can be shared between different models and, given ESM-side support, swapped for a specific object. Depending on the version they also support PBR and various other rendering features Fallout 4 and 76 introduce.