As for hollowing a barstock, I presume kamis will find no problem. I've heard so much about countryside gunsmiths in SE Asia. Guns need barrels, hollowed barstock with very constant diameter. There's no reason to doubt Nepalese best kamis can't do much torelate jobs on knife handle.
Modern daisho idea sounds nice in terms of convenience. I just want to call it in other name.
Though I don't remember those very old days, but daisho was strictly prohibited to non samurai persons. Dai, big, means katana, and sho, small, means wakizashi. Government was not very strict against wearing a katana on ordinary people. But not daisho. But a wakizashi combined with katana was only allowed for samurai for it was the executioner tool on himself. They thought those who go as a jury and an executioner mustn't exclude himself. Some just didn't do so, some only thought he could do so, and still some proved it.
An odd but somehow rational sense of fairness IMHO.