Problem is, without history, we have no way to tell what players can do and what they cannot. We know how many men England could field in 1200s or 1900s. But we have no idea how many "Destiny" class interstellar destroyers can Yliria Confederacy field. So massive set of rules and mechanics would be needed to make it work in logical way - rules concerning economy, warfare, society, etc. And of course GMs work to make world coherent would be huge too - after all it's SCIENCE fiction. But if you say you could make it work, you have my sword of course.