First, I wonder if it is worth asking for all firearms to be disassemblable... disassembleble... capable of being broken up for parts?
If the game allowed this, then rather than have to store obsolete weapons because they might become useful in the workshop later, break them up and store the bits.
Need 5 autopistols for a workshop recipe? No problem, just have 10 Pistol Parts and 5 Gun Parts in the vault instead. This may have been suggested before, if so, sorry. I forgot to check.
Second, I love the way that certain weapons get a power boost depending on user stats. Since what we have there is the weapon power being controlled by something that is not inherent in the weapon itself, is it possible to have the game allow a more freeform way of manufacturing firearms. I am thinking of "get x heavy shotguns, weld them together, power (and weight) for that particular gun is (damage times x number of barrels)."
I dunno if this is possible, it might involve the game adding weapons to the master list on the fly, but I can see the gals personalising weapons from the stock, giving them names and so on.
Third, last and easiest. Volley revolvers and ducks feet. Before proper mechanisms for rapid fire, gun makers just added more barrels which the user could fire singly or all at once. I can definitely see Derringers, ducks feet and volley revolvers fitting in as one step upgrades to the small revolver, flintlock pistol and 6-shooter.
p.s. Please do not take these suggestions as any sort of criticism of the mod. I really admire the work that has gone into it and feel bad about asking for more