I think your concerns are a bit... exaggerated.The whole idea that combatants are aware in a 360 degree field of vision at all times is just...so backward and terrible.
I don’t want facing rules, but I draw the line at pretending that the completely absurd notion that an engaged combatant is hard to sneak up on makes any sense.
The PHB (p177) says:
I certainly don't read that as "360 degree field of vision at all times". Does anyone?In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.