That's right! An idea for a mod that adds weapons based off of Custom Enemies!
Here's a list of what would be my take on Custom Enemies' Weapons:
HD Enemy-Adding Mods:
Ultimate Enemy Pack(HD):
Zorg Grenade Launcher:Acts similary to a shotgun,but shoots small grenades! Useful for large groups of enemies!
Arachnocod's Antenna:Shoots electric mines that home in on enemies!
Royal Guard Reptiloid's Hand:Shoots magic seeker blades!

Remastered Enemy Resource Pack 2017:
Magic Kleer's Head:Shoots Magic Balls that cannot be destroyed by enemy bullets or projectiles!
Magic Demon's Hand:More Powerful version of the Original Demon's Hand,but shoots magic balls that cannot be destroyed by enemy bullets or projectiles!

Hardinger's Enemy Assets:
Biomech's Spawner's Larva Launcher:Shoots friendly larvae that will seek in enemies!
Zorg Slimer's Acid Launcher:
Lightning Reptiloid's Hand:Shoots Balls of Lightning! Their explosion deals damage similar to the HD Cannon's Cannonballs,but has a large explosion radius! Although Lightning-themed.

BFE Enemy-Adding Mods:
Ultimate Resource Pack(BFE):
Biomech Seeker's Rocket Launcher:Shoots missiles that home in on enemies!
Arachnoid Wizard's Gun:Shoots magic balls at a moderate rate!
Electric Spider Gun:Shoots a electric laser!

noam 2000's BFE Resources:
Zombie's Shotgun:Acts like the SS3 shotgun,but has bigger spread with more bullets fired,but has a slow rate of fire
Orc Rocketman's Rocket Launcher:Like the SS3 Rocket Launcher,but these rockets deal more damage,but shoots at a slower rate of fire!
Orc Sniper Rifle:A sniper rifle that shoots laser projectiles!
Zombie's Minigun:This minigun shoots at a slower rate,but its bullets deal more damage!
T-Mech's Rocket Launcher:A very powerful version of the SS3 Rocket Launcher,very powerful rockets,but very slow rate of fire.

Thana's Old Enemy Pack:
Guilty Reptiloid's Arm:This weapon shoots dark-themed fireballs,but its ammo capacity is a little less than the Original SS3 Reptiloid Hand's Ammo Cap

So there you go,I hope you like this idea! If you do or not,let me know in the comments of course! I'll keeping adding ideas for idea as much as possible,okay? So stay tuned! ;)