General thread for hacking together new weapons from the original images:
(image blown up 400 percent with pixel resize in PSP for clarity at modern web resolutions)
Essentially, take the heavy cannon, and turn it into something more like a 40mm to 50mm grenade launcher (aka M79 Bloop Gun) but with a semi automatic capability.
Quick and dirty stats:
Weight: 10
Snap: 30% TU (Acc 60%)
Aimed: 80% TU (Acc 90%)
Ammo Weight: 4 or 5?
Ammo Damage: 50~
Ammo Count: 4
The AP round is changed over to a knockout gas round that provides 35~ stun.
Taking away the AP capability of this weapon slot gives players more reasons to use the Auto Cannon / Rocket Launcher to deal with Mutons early on, and it also gives X-COM a ranged stun attack from the beginning of the game, but is clearly inferior to the alien Small Launcher.
[Perhaps eventually a survivability factor could be coded in for stun weapons it so that different aliens have different reactions to each weapon. For example, all the races in the game have a 95% chance of survival if stunned by a Small Launcher; while Sectoids are 90% likely to survive being stunned by human knockout gas, and Etherals only have a 5% chance of survial. This makes acquiring the Small Launcher even more useful.]
Right now there's no real reason to pick the heavy cannon, unless you know before hand you're going up against Mutons without plasma weaponry; relegating the weapon to a very niche role.
The Grenade Rifle replacement, in addition to filling a hole in X-COM's human inventory (ranged stun), would provide a relatively lightweight explosive/inciendary weapon to your troopers that would complement the heavier autocannon and rocket launcher.
You'd be able to hand it to your generic troopers, instead of having to search for those squaddies with beefcake stats who can handle Rokkits or AutoCannons to provide hanging back covering fire.
