Two points, you can't add AP guns anyways unless you already have AP and you can't add capsule guns either since they are server sided. That only leads you to add the guns you can already buy in the shop.
what is the point of gunadding IF they require the level requirement? Might as well just buy it in stores. I mean you could add the Noel stuff but no point realistically. Only thing worth is the anaconda or barbatos but they don't work so.