It is not just about the looks.
It gives you an operating mechanism like bolt action ARs for those who like to use lowers for everything.
one could use 380 cases with magnum primers to provide reliable ignition.
Or machine a few stubs with the same dimensions to use shotgun primers.
On top of that is very simple to make one since one doesn't need any dies to cut the chamber.
I am not inclined to ML but a 35 or 45 caliber would be interesting.
It is like a .410 shotshell and 45 colt upper, simple and it could be fun.
That's silly. Since it still uses a normal lower receiver that needs a background check just like any other gun, build yourself a nice bolt action in any caliber or use one of those bolt catch locks if you don't want a semi auto function...