Has there been any thought toward modeling forms or types of government? This could have a significant impact on the way a game plays out.
For instance, if the empire was run by a despotic or tyrannical emperor, all industry might be state controlled. This would have obvious pros and cons on the economy, military, research, etc. Similarly, there could be monarchies with feudal systems, which I think would really enhance role play. You could appoint officers as colony governors, grant them territories and titles and at some point, they could evolve into NPRs. There could even be a dynastic element with family relations, children, political marriage, etc. Something along the lines of Crusader Kings.
Not that Aurora needs any more complexity, but there would seem to be so many intriguing possibilities...mega capitalist societies, oligarchies, democracies, theocracies, etc.