Ok, I think I have the blender GR2 export version working now; turns out I just needed to use the X-Flip skeleton option to solve my model/VFX mismatch. Praise gilgamesh
So import .GR2 unpacked with LSlib, arrange your model to that skeletons pos, use Armature modifier (Relations tpye -> Armature, Parent Type, Armature). Also used vertex groups with the same name as the imported vanilla weapon's mesh name (WPN_HUM_Flameblade_A_2_Mesh in this case). For the second mesh I used one of the bones used for a LOD so will have to think about how best to go about that. Hopefully we're not limited to finding an existing skeleton that fits the modded weapon closest.
![[Linked Image from i.imgur.com]](https://i.imgur.com/sT2OStp.jpeg)