I'd love to see a modern cartridge conversion on the LeMat but I doubt it'll ever be produced. It'd be a niche within a niche.
I've seen pictures of an original LeMat percussion pistol converted by the factory in France to fire pinfire cartridges. They also produced cartridge guns.
Here's an article on the gun Johnny Ringo used.
http://www.johnnyringo.net/lemat.htm