One of the biggest problems I've noticed with this game is how fleet upkeep works.  While it makes sense to have upkeep drain a percentage of a resources as your fleet gets larger, the opposite should be true as well.  The upkeep percentage should scale with *current* fleet demands instead of just increasing based on what your researched and permanently draining your economy.  The problem is most obvious after a large fleet battle where one or both factions involved lose most/all of their fleet.  Suddenly, the fleet is gone but the economy is still hamstrung to the point of being unable to rebuild it.

Anyone else think it would be better if the upkeep system were changed to reflect current fleet demands?  It would be as simple as changing the upkeep system so that the research just unlock higher upkeep levels for use but current fleet supply used would govern the actual percentage of the economy that got taken for upkeep.  Warcraft 3 (which many elements of this game seem to be modeled in a similar fashion to) used a similar concept for upkeep but when your army died down the economic penalty went away, giving the side losing a battle a chance to maybe rebuild and still win the game.  As it stands with sins once you get to the later upkeep stages and you fleet is lost there isn't much chance your economy will be strong enough to rebuild it before you lose the game.