Two quick notes on the April/May campaign:
I have a neutral humanoid race that develops crude firearms: a pistol equivalent and a musket equivalent. They are not magical and they are not necessarily high quality, either. Use of them marks a character as Chaotic in alignment.
Making a class for a type of gunslinger (haven't decided if it's NPC only), I looked at the PFSRD for ideas. I like the idea of grit and I can nerf/alter some of the Deeds that spending grit allows.
I decided to try setting up my gunslinger class like the Unearthed Arcana Mystic class. Grit points are used to use a list of Deeds. Spending more grit points on some deeds up the effect.
The other note is that I'm going to provide the option of Usage Dice for arrows, bolts, stones, and all other forms of ammunition. A player can choose one or the other. They can only switch between sessions.