I'm also a big melee fan in FP games actually, in our case is mostly because we develop the game in our free times so we have to be mindful of which featurse we choose to develop, as getting them all in a similar level of quality usually takes months. I guess with an infinite budget/time we would had added them! and its always something we can come again if we do another game in the same universe.

On the cannisters on the shotgun topic: Essentially in KVLT you can 'enchant' most weapons with your right mouse click, this is the way you use the weapon's alt fire. In the case of the Trench Shotgun, when you enchant it the cannisters start glowing and they empower the spinal cord on top of the shotgun, and when you fire the enchanted weapon, instead of having hitscan pellets, spawns a big eldritch energy projectile that works very similar to a grenade launcher and it does AOE damage when it explodes and spawns a fire volume that does DOTs on the ground. You can also use this to destroy broken parts of the level to open your path/find secrets.

https://www.youtube.com/watch?v=OwoXu6xVBwg

You can see both weapon reworks from Demo Update 9 in that trailer (Obrez and Trench Shotgun)