Flintlocks in a Mod?

It's possible to mod this in. You could easily create new ranged weapons and new techs to unlock them. The actual coding would be really easy. The models and animations for the guns would be by far the hardest part, and outside my skill set. I'm not sure but you could probably add a sulfer resource as well.

The problem would be combat speed (does a combat speed below 1 mean you attack every other round), simulating the inaccuracy, and so on.

I do think gunpowder should be in Elemental though at some point.

If you want to simulate the accuracy (or lack thereof), can't you put an accuracy modifier on the weapon? I seem to recall the basic bow having -accuracy as one of its attributes. Also, you could perhaps do something like spells do and have the gun use up all of the available action points every time it is fired.

I don't think that you can make the action point cost so high that you lose a turn 'for reloading,' but I suspect that you could make it so that firing the gun casts something like tangled web (the spider ability that prevents your unit's next turn) on the gun bearer and have the text that shows up above the unit on its next turn read "reloading" instead of "tangled web."

Making a weapon into a ranged weapon requires unlocking a ranged ability for the weapon. For example for a bow it is usually:

 The BasicBowAttack ability is essentially a spell that is used as the basic attack for the weapon. Creating a new ability, effects etc and unlocking it as a new ranged action is pretty straight forward. I've not tried it but in theory you could add the cooldown tags to the ability you are unlocking which would make it usable only once per cooldown period. Which would simulate reloading taking a turn or more.

The XML is no problem, however there are no unit animations or models. That will require a significant effort on your behalf to learn.

I hope gunpowder does get added in even if only as a minimod.  I can see good applications for it, and not just for dwarf factions or Ironeers - my sci-fi faction could do well with flintlocks, since they'd know more about gunpowder than some other faction who would be researching it, it'd be just a matter of rediscovering it.  Same thing in the Warfare tree though, I'd imagine.  However...

Still, I hope that someday gunpowder weapons in Elemental will be a reality.  Good luck with that extra stuff with modelling and that (or finding someone willing to help), Apoc, I'd be hopeless at that personally, sorry