PLEEASE, PLEASE let there be gravity in EV3. that would be really cool, and not too hard to program. That would make it really really cool.
Of course, some ships, like bulk freighters, are heavy and have weak engines. you could make an outfit that would show the radius around large objects where the engines would be insufficient to escape. Kind of like marking the event horizon of a black hole, except it shows where the ship cannot escape from make it like a red circle superimposed over the main view or something.
Or, it could make the planets different colors on the radar depending on their mass, so you know how much gravitational attraction they will cause. It wouldn't be that hard to program it, because its the same kind of stuff as the density scanner and the IFF decoder.
Also, when a ship explodes, it should do dasmage to the nearby ships, and leave a cloud of debris that can damage ships that fly through it. Obviously, the faster a ship flies through a cloud of debris, the more damage it should take.
Having a realistic physics model is important. Normal flight should use fuel, but only a very small amount, and only when you use a thruster. There shouldn't be an arbitrary cap on speed, but rather, i would be determined by the combination of the thrust of the ship, the viscosity of space, and how aerodynamic the ship is. For instance, in a total vacuum you could accelerate until you run out of fuel, but in a nebula you would reach terminal velocity rather quickly and stop accelerating.
You could also put is an option to allow asteroids to do damage when they collide with a ship. If people could turn it on and off that would be nice.
It would also be nice to make it so you can target, shoot at, and destroy the asteroids. Like make the "a" key target the nearest asteroid or something.
Asteroids should also collide when they touch, and be affected by gravity. Like real life. You would have to make the asteroids smaller, and make them travel in some uniform pattern, like orbiting the center of the system, instead of making huge asteroids shoot around randomly at high velocities.
Also, if a ship gets caught in the gravitational field of a planet, or if it approaches the planet way too quickly to land, it should crash instead of going right through
Also, put Capn' Hector in a ship that can actually kick ass (That is, if you want to get paid 
).
If you put most of that into EV3, I will definitely buy it within an hour of the release.
--Yoda