I would like real tactical features (like targeting specific targets and planets, as opposed to running as many missions as possible in the same square until it changes color).
You could build sensor arrays to know when the enemy is near you or your territory (you will have the advantage of being able to see anything your allies can, so you won't be wondering around in the dark like SFC3, but this will allow you to see even more)
You could build trade ports, battlestations, mining stations, ship facilities, etc as well. And, of course, you can blow up your enemy's own stations. But, in order to do that, you have to deal with any ships that might intercept yours. The whole point of this is to encourage coordination. First, a small band of Romulans sneak in and destroy the sensor outpost on the neutral zone. Then a huge assault attacks and destroys a Federation shipyard and mining facility. The Freighter convoys carrying the most recent suplies to the Neutral Zone outposts are intercepted and destroyed. The Federation suffers a devistating defeat, and has to quickly transfer ships from other fronts to compinsate for the Romulan agression. The Romulans, on the other hand, establish colonies in targeted Federation space, and send materials that once headed to the Federation, to Romulan shipyards to make more Romulan ships.
Just an idea
I would like the singleplayer mission to work a lot like SFC3 (as opposed to SFC2) in that missions happen at spots, and not randomly. The added features I rambled about above would still be in place as part of the expanded strategic role. Missions would still probably appear in the hex you are in, but it would probalby be a good idea to assign/request to be assigned a mission that would help your empire.
There won't be any dv and hex-flipping. Your empire controls a hex by physically using it (if it can be used for something) or by claiming a hex nearby a used hex (these are hexes that are, without question, belonging to that race)
I'm probably not discribing it as helpful as possible, but this is one small idea I'd really like to see.