This got discussed many times, and there were also many polls, and the result was usually that a pretty significant majority of players didn't want them.
The main problem isn't historical accuracy (who cares?), but that they'd be difficult to balance (and also the devs would have to get models and stuff - I think there's only a pistol model in native).
Personally I think they'd be difficult to implement in cRPG without a lot of balance problems, and it'd take a lot of time and whine to make them fit in.
But, I think they'd be nice for strategus. Disregarding the problems of balance etc (probably would be best to make them underpowered, expensive, and rare), I think it would be kind of cool to have them show up occasionally in Strat battles and represent the first firearms being introduced to Calradia.
Maybe really, really inaccurate, glacial reload time, and xbow level pierce damage. Sort of like a one shot luck based thing out of desperation. There'd be little practical purpose in having them, but it'd add flavour. Maybe a really rich faction would buy some to show off, or for fun. And you'd have to somehow get the smoke so it didn't lag everyone.
I think firearms are a difficult thing to introduce, and it should only be for flavour, not for a serious weapon class.
