We also need to take into account the fact that James, at the very least, is in pretty amazing physical shape for his age having been in the Gallian Army. I can't speak for the rest, though I imagine Kyo is in comparatively good shape, but he's also not a Scout XD Anyways, the only real issue is that sure he can carry it, or another scout, he can aim and fire it, but that kick is going to do him in and his aim is likely to be completely off because of it. Essentially, it comes down to anyone can fire the weapon, but only those trained in it are going to have any semblance of accuracy.