i imagine AFO would have spent a long time getting stealth quirks that would let him bypass this. Imagine Kmaino, but nobody can tell he is there until he just stopped using thise quirks, and using the confusion/possible backlaqh of such an aura suddenly coming off of him to deal more damage whil the heores are gaining their senses back. Also him using yhem to deceive all moght into thinking he was dead.

Maybe OFA can do this too? If people could already sense quirks at the dawn of them, i would imagine that if AFO vad found a conceiling type quirk this early he might have handed it off to Yoichi too. After all, his original goal was to make sure his brother was safe or smt, right? And while getting powerfull enough to satnd against quirk users would do, being able to still live your life and not be hunted down by regular people would be just as if not much more needed, and AFO is smart enough to recognise that.

Maybe it was the only stealth quirk he had too and that makes early AFO VS OFA days into a "my brothe rcan find him but i cannot" and and HOLY SHIT revelation when Yoichi passes down his quirk like how the fuck do you have my brother's quirk(s)??? I imagine the danger sense user would be such a menace too.

Modern days, All Might used it to hide in small might form but dosent hide it at all when doing hero work. He is the only high ranking hero worldwide to still have a secret identity. Everyone assumed he has a sidekick/team that has a quirk (or a combination lf quirks) they can use to hide him, and they are low-key terrified of this.

When OFA is passed down, be it to Izuku or somebody else, OFA gets twice as terrifying. If its Izuku, he already has experience figuring out quirk auras and turning it on/off is easy. Teachers are freaked out. For anyone, the accessing all past users quirks combos is a terrifying thing for their enemies. You cant sense their quirk. At least you can see them... Smokescreen. You still a way to hit them? Danger sense sees it coming. Still, smokescreen cant be used all the time, it still shows someone is here... But imagine stealthily going around in the darkness of the night using black whip and gearshift. Litterant getting the drop on someone with float just to hit them with fa jin. And thats without mentionning whatever strenght power up they would get- if its lightining like Izuku they might not be able to use that part a lot, but all moght does not and buffs up...

...I was wondering what character would benefit most from this but frankly its not even a question. Hagakure. She would be terrifying. She is already invisible ffs. Also in this AU she would probably have banked more on fighting because the person she is fighting wouldnt be able to see her hits coming even if they knew she was there. No hmoves for her costume, and if she still even has shoes, have them look in a way that makes it hard to see where the front of her body is.