i suggest changing the "save server preference" feature that connects server type with individual player to a server preference by territory area on the map
lets say half of the map be played in NA perfect time and on NA servers, while the rest of the map being played in EU perfect times and on EU servers
this will keep community on one map, just making them to change their "claims", and NA/EU clans would obviously want to sit on the border of those two different timezones areas, where EU would be dealing with stuff on one side and NA on the other
EU conquering NA or vice versa would still be possible, but you couldnt really complain about hour the battle takes place as its your choice to move into that territory