Something akin to COD or Cyberpunk where you can manage attachments and parts.
If you add an in-game bench to the map, where you can drag and drop parts and attachments, as well as removing certain gun parts, it makes it feel more immersive when you're the one doing the action and not in a menu.
You could even make the guns function without certain parts, like no stock or no barrel, but it would effect the firing.
maybe even a sawed off tool but thats just hoping