Player control indicators
So this goes along with adding the ability to see the latest planet information for another player without having a ship actually being there (which has been mentioned in other threads):
The biggest problem I have with this game is that there are very poor visual cues. It makes it hard to flesh out a sweeping strategy when you have little visual information to go by. Think of the Civilization series. They show you clear boundaries where your civ ends geographically and another begins.
Obviously the way we think of boundaries in EotE is different because you can simply circumvent someone else's sector to get to your sector behind it. But I would like to be able to see some basic information about mine and another player's area of control. By using the information discovered as to who owns what planets, add the ability to click on a player from the Relations list and see which sectors they currently (according to the latest information you have gathered) have planets. This could be shown by having a zoomed out sector map (the 25x25 one) and flashing red on whatever sectors they have planets.
This could be made even more useful by adding another level of cooperation to the relations menu. By adding some kind of feature that allows players to share map data, it would allow a player to more accurately determine strategy based on current control of the map. This brings about a problem with people sharing data inadvertently with the wrong people (eg, A is friends with and shares map info with B and B is friends with and shares map info with C, but A and C are enemies and don't want their contributed map info to B being shared with one another), but the other way to do this would be some kind of higher tier tech that is accessible in each tree that allows you to always see who owns what (but not necessarily what ships and orbitals are at each planet). Think of the GPS technology in Civilization which gives you a constant view of the entire map. It may give away where you are, but at that point in the game, it is necessary to see what's going on to have a somewhat competent strategy.
But first things first: allow the ability to see the name and owner of a planet after you have been there. For crying out loud, this is the age of interstellar trade. I should be able to remember the name of the planet I just visited.