This has been a ton of fun. I first tried it on the big single player map Cheogsh, and it worked quite nicely there!
Funny enough I learned about the upgraded shotgun after I beat the map and began killing foes in the vanilla 02 map that came up, which got me to look for the official rust and bones page to learn about the others, a very cool touch!
I look forward to trying this in another map with fairly tough enemies.