There is indeed a grenade launcher out there. I thought that was what we were talking about? Having different grenade launchers with different amounts of "kick" to them.
Grenade launchers are infantry weapon, no more necessarily OP than a rocket launcher. The XAE has a version of the grenade launcher, which is taken from Riiskelini's "Guns and gadgets" mod and modified to balance it a little. I'd suggest trying it. It's a really cool weapon. Awesome to be able to have "artillery support" for your soldiers early on, and less outright OP than the blaster launcher/mind missile with their multiple waypoints.
It is not a super easy weapon to work with as a modder since it is a powerful starting weapon. The arcing shot does make it harder to miss (being a tile off with a pistol shot is a bad miss, hitting the floor a tile away with an explosive, who cares?), so it does need to be balanced carefully by accuracy/TUs/damage so it doesn't become the one weapon to rule 'em all. But once your soldiers become more accurate, a good sniper or even a few shots up close are usually a better solution. It is difficult to get line of fire in crowded maps anywhere but down streets (so terrain pack helps balance it) and a simple roof will protect you. It's also useless indoors.
Any ways, if you guys use it, let me know!