What kind of game are you thinking of? Is it text-based, like:
"You are in a spaceship, travelling North, slightly upwards, in some arbitrary frame of reference. A vastly superior enemy is instantiated by Math.random() and the default ClassLoader within atomisation distance and converts you to your component elements, only travelling away from each other at a much greater speed. You are dead. You have completed 0.001% of this adventure."
Or is it multi-player FPS with full-immersion VR? If it's the latter, adding enemies is much easier: you just need to write a really, really good game, spam links to it onto a few blogs, and your enemies will download it and do their best to destroy you from the comfort of their mothers' basements. Or cellars / loft conversions as appropriate.
I think we need more info to answer your otherwise very interesting question.