Since it's for the foundry, there are ways in the foundry to block enemy view without hiding them. I don't know all the tricks they use, but I've seen invisible walls used for that often, but a few missions I've played that doesn't seem to be the case, since I can approach and fly/walk around among red map dots, but can't target or fight them until some dialog or interaction. It'd be best to ask in the foundry section to see how other authors have done that.
Limit in the game mechanics means the enemies can ALWAYS see you, they know you are there, cloaked, far away or not. Enemies are just not allowed to attack you while cloaked, however if they get set off on agro they'll beam straight for you ignore the rules of engagement. It happens in ground often, in space less but you can still see it.
I know there are ways to use invisible walls, but , I had the idea that you could run overhead enemies and they not see you. but make it where they'll attack you if you fall from where you're running, so invisible walls aren't an option for that.
I probably should have mentioned it was for ground purposes.
About a year or so back, Gozer indicated Aggro range was 15 KM... though that seems to have decreased.
Aggro range is different from perception range. Agrro range dis how far you need to get before your are removed from the threat tables of the NPCs. (i.e. They no longer consider you a target).In space it's roughly 10 km. But it depends on the ship type(s). Science ships have slightly longer perception ranges.
On the ground is more complicated. Perception range depends on teh facing of the NPCs. Forward facings have "normal" perception. To the rear facing they have much reduced perception. With a bit of stealth (doesn't have to be perfect), you can sneak up on an NPC from the rear and get into melee range. And now you know one of the reasons that NPC spawns on the ground run around and stand in different directions when the stop.