Well,then this would be a proposal for SE5:
For a far more complex strategic background in the game make the economy planetdependant !
You would be forced to move ressources to production specialized planets or planets with more people than they can nourish...
You would of course need to be abled to build several ships at one time in shipyards or more shipyards per planet and you shouldn't be abled to kill planets as easy as it is now, you should need to invade them, perhaps because there is a little bit of fallout in the athmosphere, if you just bLast em up
Best would be, if SE5 becomes a mixture of the best ideas of all the web-based space strategy games out there