Game design for demo game of drupalrtsg

I do have previously implementations of games using rtsg framework, but to be honest, they are not complete, nor very well balanced or are stripped copies of online games (travian and ogame). In order to build a demonstration site I'm open the game design and goals to discussion, so feel free to drop your idea of what kind of game do you like to be testing.

Currently, http://game.drupalrtsg.net is closed to registration (in fact, there is no game installed yet). If you consider a good idea opening it so people can reserve their usernames before the future game starts to be playable let me know and I'll change the server settings.

About the game content, I'm in favor of a travian-like game, but as a demonstration site, playable since the very begining, I mean, instead of starting from scratch with an empty village, providing a minimum default army and buildings to start playing with. I'm discarding space games because internet is already full of them, and actually www.outer-core.com is an space game from a well known person (cheers afeijo) and it is not my intention to get in an interest conflict here.