This is a quick idea I wanted to throw out to INS when they get to the point of considering sensor systems.
Implement a kind of sonar. Imagine having hexagons only for friendly ships and destinations. All others require the player to spot them visually. So some sort of sensor system is needed. The game could just say that the ships have fantastic passive sensors and that they track all manmade objects constantly, giving hexagons for everyone. Personally, I would abhor such a thing.
Barring perfect passive sensors, the sonar thing is intended to bring a game of cat and mouse tradeoffs to gameplay.
When I want to see what’s around me, I ping my sensors. That triggers a spherical wave front that propagates outwards from my ship. Smaller sweep angles should be possible, controllable by the pilot (e.g. a hemisphere or less).
As the wave touches something, that something glows briefly. Ship, planet, ring, whatever. The faster the wave propagates or the farther away an object is, the less intense the glow on anything it hits.
The color of the wave fits a spectrum of colors. Red for close objects and on through to blue for very far away objects. Each color represents an entire order of magnitude of distance, allowing me to roughly estimate how far away various objects are. The timing of the wave striking them and making them glow will also tell me that, but the color spectrum is suggested as something that should be used in all ranging feedback that the player sees.
Ships can generate varying range pings (faster waves) and varying power pings (makes objects glow brighter). A fast wave makes discerning range more difficult, but if an object is 1AU away, you only want to know that it’s there. A low power ping makes spotting anything more difficult, but it helps to mask you as the pinger.
On the flip side, if I ping you, you will see me as an intense flash of light. The intensity is dependent on how far away I am from you, the power of the ping, and so forth. Generally, pinging is a way of giving away your position - if anyone happens to be looking in your direction and can separate your ping from background light.
In the interest of data tracking, only allow ping waves to travel for a few seconds, and only permit one at a time from any given player. It may be that many more ping waves are possible at one time, but just one should provide a lot of gameplay.
Fake ping generators would be a way of redirecting a player’s attention.