We call that a royalty.
Sounds interesting please develop this idea a little further. I have also thought of an accessory for the back carry water bags. Many of the Local Marines damage their bags in the field especially around barbed wire. I have always wondered if a hard Kydex shell to protect the thing might have a market. A "Turtle back". Combine that with your idea and maybe ?? we would have a whole new line of … what do ya think ?