High capacity in a lever action is generally 14 rounds in a rifle or 10 rounds in a carbine. Other than being in a serious gun fight against several determined assailants, that will be more than sufficient. And it was quite sufficient even for that in the days when the Henry Rifle and the Winchester 1866 and 1873 rifles were still young. As the Indian Wars drew to a close, the lever-action rifle evolved to accept longer, more powerful cartridges with extended range. Although the longer cartridges reduced magazine capacity, it was found that game animals rarely stand still and wait around after the first shot. Half-magazines and even button magazines began to be popular because they shot as well, usually even better than the full-magazine version as the range increased, plus they weighed less and the extra capacity was simply not needed. By the time of the First World War, the lever-action rifle was obsolete as a military weapon, with the possible exception of the Russian-contract 1895 Winchester, but it too, loaded from a stipper-clip. So, to answer the original post: Even if you can build a working prototype, it will be virtually unmarketable. I could imagine that the working prototype could eventually make it's way on screen in a sci-fi film, but that's about it.