Multiple continents that force server for real world locations would be so COOL.
The continents should be similarly sized, but the terrain should be different.
If items required terrain specific resources to produce (wood-forests, metal-mountains, wool-pastureland, etc.), and the world map terrain translated to the battle terrain, then over time the continents would evolve different fighting styles.
My underwear is now sticky thinking about it.
Like, if the NA continent had lots of steppes and plains, then horseback combat would dominate; if EU had lots of forests and hills, then archery would take more precedence. This would be a general trend though, not a necessity.