Teleros wrote:..the orbital station can't move, so the enemy can ignore your fortress worlds if they want, because your fleet is smaller due to the money being spent on fixed defences.
The personality of the Emperor would decide if the Empire is be more defensive with battlestations or offensive with fleets of starships. Both are fine, but nobody should not be able to keep building both without some kind of limit.
Money itself should not be the only limit. If it was only about money, then why bother about culture, politics, relations? It is not satisfying enough to only get rich and keep building ships. It's all about balance for all aspects of wining conditions.
Strategy game like Civ V Brave New World show perfectly how it is done.