Good luck with your business, I like the idea. I know some guys who wanted to start BMXing but gave up (and moved to MTB) because the bike was simply too small for them.
What selection of tires is available? It looks like dirtmonsters in the pics. I can understand that rims can be made no problem, it probably mainly means re-adjusting of bending radius of extrusion that the rim is made of. But for tires you need completely new mold, which apparently can go up to 10s of K usd.