They were in the last games of the LS series, why not here?
too many have said that they would be overpowered, and in part they are right, so what would make this one different from the rest?
simple, a new variant of explosive weapons, active (so they have a limited number of uses), and with a range limit.
now, the big difference between the grenades and the launchers would be that grenades tend to roll and take a little while to explode, a proyectile from a launcher would explode on impact.
now some basic stats:
lvl 25 (since explosives go with a 5 lvl gap each)
Damage vs Buildings: 100
Effective range: 3
Carry limit: 2 shots
Damage vs Buildings: 400
Effective Range: 5
Carry limit: 1 (single use launcher, once used players would need to craft/loot another one).
The lack of a "Detonation Time" is because these explode on contact with an enemy/obstacle, and like the grenades, they wouldn't go far past the range limits (following the "aiming to the floor", to cause as much collateral damage as possible).
killing zombies with explosives would be a tad easier, a good thing since there will be stronger enemies soon in the game.
just like with grenades, players could shoot to any place on the "aim ring"
arming a group with nothing but rpg's for a compound raid would be a terrible idea, since all the rockets would explode before hitting the targets (if they are past the 20 range).
more variety to the current arsenal
they would be an excelent multi-purpose weapon (players shooting to broken cars/thrash containers to kill nearby idle zombies outside of their weapon's effective range)
like the other explosives, there could be craftable improvised (somewhat less powerful) variants.
Explosive charge flies a lot faster, Lack of a fuse (sometimes a few zombies of a group have enought time to get out of the effective range of a grenade), some (if not all) the grenade launchers could use the reload animation of the sawn-off shotgun, explodes even if it didn't had a direct hit on an enemy, rocket launchers wouldn't need reload animation at all.
Rare, Really loud, while aiming it the character must stand still leaving it vulnerable, if something gets in its way it'll explode (possible damage to the user if its fired to a close target), they would require a brand new system for its working, hit detection and other complex technical stuff.
feedback is welcome.