Agreed. Beyond a more accurate sculpt and better robes, the body proportions are the other main area of improvement. But other than the tailoring perhaps being more labor intensive since the fabric is more delicate, it's really the R&D that needs more attention, not the production cost.
Thanks! The base is a HT Vader, with the body heavily modded and the bodysuit resewn. Robes made with better fabric, kaiyodo helmet, hurricane dome, and you're essentially there.
You can check out my customs thread in my sig if you want to know more (and see more pictures).