I think this concept is interesting. It certainly gives a cartridge much more versatility without having to go out and buy another rifle.
Or perhaps going heavy for caliber and not giving up velocity.
Interestingly, I built a .308 with a 16.5” barrel for a dedicated silencer setup. Compared to the original 24” barrel the rifle came with, I’m giving up some 200 fps. Now, the deer out to 300 yards don’t really care…but if I wanted hunt longer ranges (backpack sheep or whatever) and needed to get that velocity back, this idea is pretty cool.
On the other hand, it also means not needing to buy another rifle. So where’s the fun in that?