No, sorry to dissapoint you, but it’s not possible to do that.
The closest you can come is to have the same number of weapons and just replace the weapons with other ones, however in the game it would say the old weapon names and not the new ones. Another option is to just make new skins for the current weapons.
Other than those 2 options, you really can’t do anything with the weapons without your own mod.
Now with that being said, I think NoQuarter may still be open source and looking for developers. SO if you want to help out with that mod, I’m sure they wouldn’t mind. Also ETPub is open source, so if you want to have ETPub with new weaps you can start there also.