I really don't think this is a problem to worry about. In any election there are always some voting patterns based on demographics and personalities. Of course these skew the results, but it's not always a bad thing.
In this case I think it has potential to be good. I think there is slim potential of a negative outcome (such as an under-qualified candidate being elected) and quite a bit of potential to work in SE's favor. SO in particular has a vastly multi-cultural user base and having moderators with insight into local cultural issues can actually be a good thing. SE sites make the Internet a better place when the elected moderators understand both the SE engine and how to best leverage it's strengths and the needs and culture of the target community.
Lets look at this another way. Forget the regional and cultural issues for a second and just look at the area of expertise. Lets say elections are happening on Christianity.SE (where I serve as a moderator, so I'm aware of some of the issues). Of course the SE engine works pretty much the same over there as it does here, or on SO, or or TeX.SE. But where should SE go to look for moderator candidates? Should they hit up the user roster on TeX.SE for people that know how the QnA engine works?
While there isn't anything wrong with that as far as it goes, there is no particular reason why that would qualify them as a good moderator. You want somebody that knows the subject matter at least a little bit. So do you go hit up some seminary and pass out diamonds to theologians? Sure they may know their subject matter, but does that make them good moderators? Are you with me so far? Do you see why those two sources are not necessarily where you want to look for candidates?
Now to bring this round to diversity.
What do you look for? You want people that are suited to the task at hand. You want them to have an eye for cleaning things up, leveraging the strengths of the platform and keeping it from getting side tracked. But a large part of this task involves people. It involves dispute resolution; it involves communicating the site guidelines to people who don't understand them; it involves redirecting people to make them better participants and culling out unhelpful content without starting wars. That takes some knowledge of people in general and the specific cultures they come from.
On C.SE our differences are less regional and more theological, but we've long since discovered it's a huge advantage to have whatever moderator best understands the belief system of the problem user be the one to handle major disruptions. When some know-it-all Reformed guy comes along and starts bashing on questions in the
catholicism tag, it works a lot better for me (who can say I agree with their theology but not the way they are treating the site) to point out their error than it does for the mod who happens to be a Mormon to do so (who wants to be corrected by someone they believe to be a heretic?). Likewise when somebody from a minority sect starts raving about how 'we must be deleting answers just because we disagree with them', people hear it better from the Mormon when they explain that's not really the problem, the problem really is their answers don't match the question that was asked, etc. etc.
People hear correction better when it comes from somebody that they think can identify with their world view. They just do. To a large extent this holds true for language and cultural differences too. I'm no stranger to the issue. I serve a pastoral role at a church in a country where I am a foreigner, and have done so for nearly a decade. I'm familiar with how people receive advice, correction and directions. And, while I'm fluent in the language and close to the culture, there are (and always will be) those moments when people just assume I can't understand. And to some extent they are right. I can preach the same message as a local pastor might, and there will always be some situation where my message will fall on deaf ears because they just can't relate to me (or assume I can't relate to them) but when they hear the same thing from one of their own it "clicks" that the message is applicable to them.
Stack Exchange is not a church. Heck even the Christianity site is not for Christians. But people are people. Even programmers.
If people vote for a moderator because they identify with them or think that person will understand them, they are also more likely to respond well to them; and as moderators are often faced with the cases where things aren't going right and need correcting, it is helpful if you have people that can communicate effectively and cut through as many barriers as possible. If there is a large enough demographic that will vote for a South Asia based moderator because they identify with that person culturally (even if it's all in their heads!) then having that person as a moderator could be a really useful thing for the site and they can accomplish more effective communications with users in that area with less effort.
So let it happen. Don't sweat it.
But do keep an eye out for the candidates other qualifications. It doesn't matter where they are from if they don't understand the SE platform or how to deal with its problem posts and people, then they shouldn't be moderators. Look for their qualifications (or lack thereof) and offer feedback on those things. As long as those other qualifications are properly discussed and vetted and the collection that moves on to the final elections all have those, then it won't matter at all if demographics do sway the election. In fact in that scenario it would be logical if they do.
Best of luck to all, and may the best candidate(s) win!