True, but judging from the paradox fans (if the forums is a representative sample to go by), over 90% of customers are Europe/US based. Openning up to a new market would mean in a way neglecting this part of the community. While I do not argue that there may be some who are interested in the far east or Africa, I do think that people relate to their individual country when playing a game.
I'm not against the idea of openning up the world, however it does pose it's risks. Although not a completely fair comparison, but I'd be interested to know what the sales figures were for Sengokuk vs. CK (without the DLC's). The amount of Byzzie and HRE/Prussia fanboys are overwhelming.
If they do take part in such an endevour, it would either include a marketing campaign to raise awareness, or be released next to a new cash cow.
