Having some IntHiddens appear as dropdowns would be quite possible. However, that would involve the Window_GameSetup.cs code saying "Is your variable named X? Ah, it's a dropdown, handle this differently". I don't really like things that look identical from the outside (ie the xml) but work very differently on the inside. I feel like it's poor coding practice and apt to confuse some other poor sucker who comes along, which is why I didn't do it that way.
That said, there's nothing stopping me from doing it that way except my sense of taste. And there are a million things in AI War 2 development that are more important than appeasing my sense of taste, so feel free to tell me to just make it work ;-)