I am no game designer or have any qualification but I have an idea for a realistic tactical semi turn based ship to ship combat system.
Ideally it would be full 3d movement but it is likely easier to explain in 2d.
So you would have the area of space between the 2 ships. This is measured in light seconds. Therefore at the start lets say there is a 120 light seconds between you and the opponent. You therefore have the position of them 2 minutes ago.
You then plot a course for your ship. in practical terms this would be taking your ship and placing it in the place you want it. The computer would then plot the course and tell you at what time point you would arrive at that point. a line would be drawn from your current location to the end point. The plot could be adjusted by dragging the line.
At the bottom of the interface would be a slider that you can use to show where various objects, such as the enemy ship, will be at a particular time (assuming there is no changes).
Once you're happy with the plot you can hit play and the ship will follow the commands. Now as ship to ship combat in space is actually likely to take weeks (and no one wants to play that) there will be a fast forward button. If you hit fast forward the game plays out until you pause it or there is a change in direction in the enemy ship.
remembering of course that the change is course will be reported late as you have to wait for the light to reach your ship. So you know say 120 seconds ago the ship changed course you can then project its current position (assuming no further changes of course) using the time slider and you position assuming no changes of course. You can then adjust you course in response to thier adjustment. And so the game plays out.
Combat therefore becomes more about placement of the ships. It also become faster as the ships get closer. The skill will be in placement, angle of attack and speed.
If the ship engage at high speed you could add in an effect that causes the weapons to miss due to time dilation.
Add in power and fuel constraints and need to flip 180 to burn main engines to slow down.
You get an RTS style game play with realistic physic deep and complex game play.
This Could also be expanded to fleet combat creating tactical decisions on whether to attack on mass or split and when to split etc.
At the moment the only tactics in space combat is how large is your fleet and how quick can you get it into the fight. Also if you wanted a low graphics solution do it as a tactical plot rather than a realistic representation.
I hope this makes some sort of sense. I came across this post whilst trying to find a game that did something like this.