I think making nitrited paper cartridge tubes may be a problem since it is difficult to purchase and store potassium nitrate (saltpeter) from the usual sources.

Except for not being able to pass the opinion of a "stitch counter" and maybe not being N/SSA approved, the resuable cartridge tubes would be the ideal option. I have been using them for years with my black powder revolvers. At least you would not have to bite a paper cartridge.