Here's a list on other modders' custom weapons that don't use the Weapon Engine.
Heavy Laser Pistol(7smoke Tennis Red):Fan the Hammer
Flak Cannon(Unreal Tournament 2003):Flak Bomb
Chainsaw Launcher(by Pikacommando,exclusive in Planet Hitscan also by Pikacommando):Laser-Guided Chainsaw Rockets
Sniper Rifle(Team Fortress 2):Sydney Sleeper Shots

How do you like these ideas? I'm sure the modders like you would give these weapons alt-fire modes,along with lots of others that don't use the Weapon Engine at all,I hope modders use the weapon engine to make weapons with alt-fire modes! Say NSKuber,you also used that for the Overwatch Weapons,right?