>>2821182It's been a while since I've uploaded an image like this.
Warning, not for the weak!
So, now it's working as intended...but.
I guess these arm twist bones are messing up the mesh real bad. Pic related.
Also, when I try to apply the new A-Pose as the default rest pose, it gets reverted back. (My guess is, that my blender-fu isn't enough for this.)
No problem, I've exported the pose with mmd_tools as a .vpd file and applied the pose in MMD. Then the mesh got twisted there as well.
Then I've removed the twist bones, got a little bit better, but still far from good, hand and elbow bones are still weird.
Also the face is messed up, because it has hidden bones for the facial morphs.
Oh man.
Here's the model.
It's from the same modeler, has the exact same rig setup, just with a different hair and outfit.
https://files.catbox.moe/yts6qu.7z 