First of all, a coherer is exclusively an electrical device. Its used for detecting radio signals. I don't think the dwemer would need a coherer unless they needed to transmit and receive radio signals, and I don't think the dwemer would have radio unless they utilized electricity. You can make up all the crap you want if it helps you sleep at night. The fact of the matter is, they wouldn't have put in vacuum tubes, coherers, or a mains hum ambiance unless the dwemer were using electricity.
Given the fact that people can shoot lighting out of their hands, I don't think there's any particular shortage of electricity; be it from magical source or natural source. The point I'm making is that the dwemer had the technology to process and utilize electricity. Technology which is far more complex than the exceedingly simple principle of channeled combustion. The whole "high tech" argument is complexly null, in the TES fantasy setting there are many pieces of concepts of technology from all over history.
Fantasy is subjective. And the context for which guns are used must be aesthetically pleasing and for guns to be in a game or universe like the elder scrolls, guns as we think of them, would drain a lot of the "other world" feeling from the fantasy realm. It would not be the same world at all. Thus, it comes down to, whatever the game developers want is what they will make, so it becomes their world to play and tinker with... Sure we like to think the world exsists without them saying it does like artists, but that's not the case...
With all due respect, guns "as you think of them" is not how they are in history.
I wouldn't care if guns were modified to have more of a "fantasy" feel to them, the fact of the matter is there's no reason not to add guns as long as they don't ruin gameplay". If they are implemented properly, then they won't ruin gameplay or "immersion,"
end of story. If they are implemented horribly like Fable III, then thats an implementation problem, not a concept problem.