>>2593214I think I've figured out that the missing textures is something to do with the order of the materials in the PMX (maybe something to do with them occupying the same space, so the materials that you'd want to remove should be above the rest) Unfortunately this model is highly customisable so it's a mamoth task that I'm not really up do doing just yet.
With regards to the physics being wonky, you're able to fix most of these custom model issues by setting the character's physics to "All". It makes them behave better but not perfect.
If anyone's interested I've been porting some Taimanin Asagi models by this fella
https://bowlroll.net/r18/user/5008 into an english format that works in Waifu Sex Sim.