Stupid feature what came to my mind, taken from Worms 4: Mayhem: Adding a tenth weapon, wich is the weapon created by a simple weapon creator, like the one in Worms 4: Mayhem, with a gauge to don't let it to be overpowered.
And also a gun creator to create a new gun with parts of the other guns, those being Jazz gun, Spaz gun, Lori gun, JJA guns and the electroblaster. And while playing online, the parts of the gun and the weapon are already stored into Customweap.j2a or something like that, JJ2 would detect them and show them.
EDIT1: I converted the bouncer, blaster, seeker, RF and TNT into Worms 4: Mayhem weapons, I tested every weapon except the RF and the TNT.
EDIT2: I'm not counting the shields and the OEM weapons.

Screenies:
Worms 4: Mayhem weapon creator, from where i got the idea
Screenie 1, showing the gun editor