I believe that implementing guns into the game wouldn't be too difficult once you have the models/textures/ect... The way characters holds the gun, reloads, ect, would probably be the hardest part after that. You could simply make it act like a bow, but with special ammo, and increase the velocity of the ammo. You could probably even add a sound effect when fired.
Yes it's understood that this doesn't follow the lore, but not all mods are meant to. I think I'd love the idea of having a flintlock pistol, if just for the silliness in it all. I wouldn't make a serious character or anything for it, but I still think that'd be fun.

Of course, since we don't have the creation kit yet, all of this is speculation. I'd just like to note that there's no point in arguing about whether a mod is lore-friendly or not, if it's not supposed to be in the first place. ^^
Plus, on the debate on whether it is lore-friendly or not... It's doubtful that we could possibly know if it is. It certainly isn't CANNON, but whether it's lore-friendly or not can be debated forever, as we can't know EVERYTHING that goes on in Tamriel. ^^;