Since winds sound like your main problem, I'd pick a road bike with drop bars so you can tuck in closer the to the bike and be more aerodynamic. And since the roads are rough, I'd pick a road bike with clearance for tires (at least 700x32 or 35). Aside from that, your criteria are pretty broad, especially considering that you're already happy with a single speed setup. I agree with no1mad that you should start by looking at what's available locally.