the best Vader helmets, hard parts sculpts are coming out of Kotobukiya these days -- unfortunately they don't do the multi media 1/6 figures...even if the poses are weird, the helmets in 1/7 or 1/10 LOOK LIKE VADER...which is more than I can say for anything SS made in 1/6 - or 1/4...
I don't see what could be so difficult -- they are pros and they've done great work on other things, but Vader they can't seem to nail...there are references galore -- other toys and sculpts out there that are accessible...I have difficulty with the idea that Kotobukiya or Taito have the monopoly on decent vader sculpts -- heck, my "Pumpkin Parts" from Target have a better vader likeness in the helmet...