While Genuine leather or Nylon would be the perfect. I still think a 2 part sculpted boot would still work as there are alot of folds in the ankle area you could hide the seam and ball joint connecting the feet. they made it work with luke ANH and the single piece boot of Kylo. It will be less...
That! or maybe the one they used for TROS kylo :D All is good as long that they stay away from the cheap pleather they use for their vaders. The sculpted boots/belt are even a step towards the right direction i love it!
Based from some shots i dont think its the same pleather they use for vader. It looks like some sort of painted fabric to emulate leather texture? i could be wrong tho.