One of the things I always thought could be a bit better was the sensor radius of planets. I would like to see the fog of war rolled back on each planet as if it had 30 or 40 of the latest sensors. Short of building a sensor boat and parking it in orbit I do not see if this is possible. I always felt that we should be able to see farther (than we do now) with our planets.
Disclaimer: I hated the 'fixes' that the forums clamored for <and got> on sensor stacking. I play my game with them like they used to be in most cases.