As far as the ideas I have for downtown, it's just in that crosshairs area. I think that should be set aside for community builds, as I stated. Outside that, build an igloo. Who cares, right? We want it to be fun and interesting.
Just no underground/redstone stuff within 500 of downtown, and no mines within 1000. That's where the trouble is lurking.
Considering MC's rendering distance, those numbers would allow us to wander all over town and never encounter anything that junks up our FPS.