Why not craft a new map? After all, the land is only a texture with fixed position of settlements (I believe it is adjustable within website map engine)
We could make a map, with two continents, both having sandy, snowy, and green lands. One with towns with battles always taking place on EU, and other one with US (with 2-hour delay between east-most and west-most village/town within continent. If any EU faction fancy conquering US lands or vice versa, they would always (whether attacking or defending) fight on town's time zone.
Also, we could have an neutral smaller continent between dedicated ones (Atlantis?) which would have settlements available to the most populated group. Within this "Atlantis" battles will take place in the time preferred by the owner.