The Most Needed Craft Parts.

body hair (shoulders, back, arms), scars, tattoos, beret

Maybe a dumb question, but which ones? I can't think of any major Japanese stars who don't already have a presence in the game. Or are you talking about newer guys from some of the lesser promotions like modern NOAH, All Japan, etc?

Sting Crow attire.

What's needed the most, by far, is just generic parts. Elbow pads with a gap on the inside. Kickpad tri-wings, like this. Vertical stripes on the calf. Finger tape. Large elbow braces like Tomohiro Ishii. Large knee pads like Adam Cole. Boot wing patterns like Tomohiro Ishii and Shingo Takagi. Bigger wrist tape. Boot trim that includes a line down the back. There are a million and one generic as fuck pieces the game is missing that we need much more than most of this other stuff tbh.

What I do is, in the image editor, place the uncolored custom part on top of whatever piece it's meant to go on (like a Logo for Chest going on top of T-Shirt or Body Suit) and create a mask for the piece beneath it.
It'll retain the game-friendly shading of the part, the shape of the original, AND it can be colored.

Obviously, this works best with monochrome things like plain single-color shapes or plain single-color text.
Going over it with I would say the Pencil/Brush tool (set to 1 or 2 pixels, anti-aliasing optional) with a shade of gray that's visible above all the other 4 colors is a good way to add "texture" and "depth" to the logo (like how the Sneakers are done in the Foot layer or the Jeans in the Waist/Thigh/Calf layers) if it's a logo that has it.

If instead of saying "Please drive through." he said "Fuck your friends, fuck your family, fuck you and fuck anyone who looks like you." I would go every day, sometimes maybe twice.