So, no hand cannons? Hand cannons had been used in Europe since the 1300s and were the first personal firearms, not being superseded until the 1520s. They were used in the Bohemia of the 1400s, principally so during the Hussite Wars.
What do they add? Well, they allow for another ranged weapon that can penetrate plate armor, and the sound of their being fired can frighten horses (a decreasing fear of hand cannons can be another skill for steeds to learn). Finally, they’re technologically unique from other weapons in KC:D, unless KC:D will have proper cannons.
How to implement them? I see hand cannons, like polearms, being implemented as “temporary weapons”, in that you can take one and use it, but cannot place it in your inventory, and must drop it to change to another weapon. “Unsheathing” a hand cannon has you unfold the stand and plant it into the ground. “Sheathing” it has you pull the stand from the ground and fold it.
Hand cannons would be fun to use, and fun to see used. I don’t see any reason not to implement them.