I'm not sure if someone has suggested this, or if this has been done with 3rd party software already, but custom weapons are a big issue.
When I first bought this, it looked amazing. A cheap, effective, easy, and decent looking game development program was exactly what I was looking for, because even though engines like unity and cry-engine exist, and even though I have the technical skill to use them, GameGuru saves a great deal of time, and allows you to make fun games with all the elements you need to get good results. I learned how to use blender, how to convert and import models, and I even learned a small bit of lua in the progress. However, I quickly found out that custom weapons take WAY to much experience with Game Guru's file structure, and all I just wanted to do was make a freakin' re-texture of a sword! I realized that it'd be infinitely better if the developers of Game Guru just added in a sort of extra feature, like the model importer, but with extended features revolving around weapons.
The way it'd work is that you could put in your weapon model, select the weapon type, a projectile if it's a gun, and maybe even some other features as well, like alternate fire modes, and maybe even a secondary fire thing, like a grenade.
I know that this may not be too fantastic of an idea, but I feel like customization is incredibly important, and should be expanded on as much as possible.
Thank you for your time, and I'm sorry if my wording wasn't really great. At the time of writing, I'm kinda tired.