Metallica… S&M 
I think it’s insteresting idea and from the start it was clear to me that it’s just an idea-to-be-taken-if-interested rather than “they should do that”. 
Anyway, I don’t think that Warhorse was doing KCD for the love of the games only, they’re not Samaritans. But yes, they believed to their original and uncommon idea so much, that they risked it, which is not common in such big game industry.
With the different game genres I can say that not every game developer stuck with one only. Remember guys that Vávra was main brain behind Mafia, he helped a lot with Mafia 2 and if I remember correctly he was also working on Hidden & Dangerous. I also believe that there are Warhorse memebers who worked on another game with different genre - Operation Flashpoint.
That’s a good example of different genres where these people were working on and Vávra personally was working at least on three of them. So from this point of view I believe it could work out and there wouldn’t be a problem. But I personally think that the idea will not be taken. It’s maybe too risky even for Warhorse…
Here’s the issue. Now take me for example. I like wargames and I play wargames (computer wargames only). And there’s a company called Ageod which is my favorte company who makes wargames. And everyone asks, “Why don’t you make a wargame about XYZ?” Now, these guys make wargames because I assume they love it, because I’m pretty sure they haven’t become rich off of it. And their reply is “The reason we do American Civil War, Napoleon, etc. is because we have to take into consideration our customers and most of them want these wargames.”
Meaning, they can do niche games (and they have) but niche games don’t make as much money, and whether you love doing it or not, you have to make enough back to keep going. And that means that you also get paid a salary and have some left over to start new games and other expenses. So, they develop a lot of American Civil War and Napoleon games.
I think KCD would see your proposal as interesting, but not enough to take a risk. Game developers have gone out of business when developing the “wrong” game.