I wouldn't even consider making any unless I could find a type of leather which lays flat. The first thing I'd do is ask a major leather supplier for a suggestion. My guess is that the softer the leather is, the more likely it is to always lay flat. That might have the disadvantage of not being able to stay firmly in a rolled up state, which is also a disadvantage of the silicone boards from what I've heard.
I would be interested in a leather board of your making. My board preference would be a darker green with tan for the board colors though. I think it'd make a great project and could be a good seller! If you could make a standard 2.25" square board I'd definitely inquire about purchasing one, maybe two depending on the price. I need a new board soon for travel/tournament play. Let me know!
I like that set, could we have a close pic of the knight? thanks