Dang i didn't search for something like this. I'm sorry if its suggested before.
What are you thinking about possibility to hide in asteroid fields or planets or stars? When you click on any of those space body's when your fleet arrives you have options to hide there. This would be cool for AI to do, pirates could ambush convoys that way... Or player
Hiding wouldn't be always same. Bigger fleet or larger ships would lower % of "hide" effect. Fleets with more advance ships (maybe adding sensor range in ship_data.csv or something) would have better chance to detect hiding fleet (oh, yeah, when you detect hiding fleet they do not know that so you can surprise surprsers) and it would depend on behind what you hide, so asteroid belt would give large hide bonus to smaller ships and fighters/bombers and small or no hide bonus to bigger ships, planets would be neutral - no bonuses and stars, well they would give bonuses depending on armor value, higher armor bigger bonus (those are hot so ships with ticker armor can be closer to it and that way hide better). Something like that.
And when hidden there should be something that would indicate how good or bad is it (just visual thing for player). Not numbers, some picture like eye. Widely opened would mean bad hiding and close shut would mean good hiding and half open would mean so-so hiding.
And there should be slight change in system map visibility mechanic. Now, fog of war would be too much but flickering (fleet disappear and then reappear again). More distant fleets from your fleet would flicker more and longer and more closer fleet would flicker less and shorter. There would be maximum sensor range of your fleet. In that sensor range there would be no flickering. Flickering thing is only because of player, to make him unable to see when AI is making ambush.
So, what do you think?