If you like the modular guns systen, why not try making more parts?
Pick an unused sprite from icons/obj/items/cet_guns, or make your own, or edit one of those.
Go to code/modules/gunse/modular_gun_parts.dm and add some more parts!
optionally, you can make new prebuilts in modular_guns.dm also!
Basically anything will be accepted for testing, and we'll balance it as we go