Its not invisible borders, systems have security levels for a reason, they are deemed "safer" because there aren't many threats in them, the police/military presence makes it so. Others are deemed "unsafe" because they're full of sharks. System security level is a consequence, a reflection of what amount of dangers are currently in the system. This could even be somewhat dynamic with time instead of static forever.
Actually modern RPGs are going exactly the other way around. They're dropping auto level scaling in favour of a much more plausible fixed or thresholded enemies level. Instead of everything that moves being equal to you all the time, now the worlds contain all kinds of levels of enemies. Its much more believable, lively and organic. Its up to you to decide when you engage who. But the game does not stop you from attacking a much stonger opponent, neither it hides the weakest.
Look into the Bethesda games, Oblivion had auto-level npcs, was its far biggest flaw, as soon as you level up, absolutely every other NPC leveled up with you, which in practice means the world is static, as if everyone levels up at the same time, then nobody actually levels up at all. Skyrim (and lately Fallout 4) implemented level thresholds, meaning that the different types of enemies have a lower and upper level limit regardless of your own level. There are dangerous places with dangerous foes, but even if you're a top killing machine, annoying villagers and rag tag road bandits will be cannon fodder, as anything else would be completely ridiculous.
Witcher 3, Divine Divinity, etc, all enemies have exactly the same level the whole game. This actually gives you a sense of real progression, unlike auto-scaling. Too much a threat, run away or die. If you're a god-like killer, weaklings will still be weaklings, time to go for the dangerous foes.
Auto-level is dung, most companies have realized this, but FD is going the other way around.
