I’d be against metal, because when it’s cold, it gets uncomfortable on the lap. Plus at that thickness, metal could be really susceptible to bending
Wood works for the underside (opposite of the keyboard), but constant rubbing with the screen isn’t very good. You’d have to add a rubber on the corners or edges like on a laptop. Personally, I’m not a big fan of the look and feel of wood, but that’s just my personal opinion.
Leather(ette) should work on both sides, but not as resistant to scratches as alcantara or there’s durability issue in general as others have mentioned.
Sammal I’m not familiar with, but it seems to be a limited production material, which wouldn’t really solve the production needs that we had with Alcantara. Although if the V didn’t suddenly go best seller and the whole electronics and automotive industry didn’t jump in, it shouldnt be a problem.