I think you have the rifles and handguns pretty well covered. However, you do need to add to the shotgun list.

I think you need a budget autoloader. Mossberg 930 or Rem 11-87 sort of thing.

And then a good double barrel. I'm thinking that one of those IGA coach guns would be good to have.

Of course, the best thing to do would be to rotate some guns through the rental roster. Imagine "March Milsurp Madness" or "Autoloadertober" as potential events for the store.