This looks really good! If I had to nitpick something, the white zig-zag designs on the chest and arms of the rig intersect at an angle so that they have some edges overlapping and not meeting properly:
There are plugins you can use to generate lines that match perfectly, OR you could use CSG Negatives to make them cut off perfectly.
Otherwise, this rig is really well put together, and although I don’t know anything about JJBA, it’s a really cool design!