For the Hazmat/Containment Breach AU would Danny initially try to pretend to other people that he's just using advanced Fenton tech? Not his parents of course, scatter brained as they are they know what stuff they have created and put into every suit they make. But the civilian populace. Imagine an Amity that doesn't have a Ghost Boy protecting them, but a mysterious man with in a Hazmat suit a strange presence to him. Sure he helps and is a decent enough guy, but there's something off about him. Something in the back of your head that whispers that this man shouldn't be here. The slow creeping dread of the people as they watch his suit torn apart more and more, the rising evidence of inhumanity growing and growing, until suddenly they see the void of green stars in a humanoid adjacent form, and realise that whatever was in that suit was not a man, and had not been a man in a long time.
Also, just people initially thinking Hazmat Danny is a grown man because the suit masks all identifying features like build, voice, etc, that would show that Phantom is a kid.
Sidenote: When I read that the Suit heavily restricts much of his initial strength, agility, and mobility in favour of making Danny a tank what does that mean in the future? Does Danny struggle not weighing like a thousand pounds and being figuratively or literally weightless? Does he need to learn to adjust his fighting style to stop taking hits that he cannot afford to anymore? Does the suit act as a restraining bolt on all his abilities and the moment it is gone suddenly Danny has been thrown leaps and bounds ahead of all of his enemies because he has been wearing restrictive gear and now he is free and stronger for having trained under such arduous conditions. I just love the idea that someone breaks the suit and thinks it is an instant win now, only for Danny to suddenly be able to effortlessly kick their ass.
If Danny is catapulted to an insane level of power when the suit comes of, I do wonder how he and everyone would react to this? His loved ones are probably glad he might stop getting hurt so much. Danny might initially relish the power boost but learn to fear it because good god does he not know how to handle this. His parents and maybe even a lot of the people of Amity are probably terrified about what this means now that this super powerful ghost is no longer holding back, a fear only compounded by the inevitable rise in collateral damage now that Danny has lost all of his skill in exchange for absurd power.
Okay, heck yes thank you for this.
Because the suit blocks every power he uses to dissapear afer a fight in canon, here he has to literally walk away and hide so he can change to human form and then use his, slightly better then in canon but still weak, powers to get invisible and intangible.
So he quickly finds out it's easier to not fight in sight if possible.
Combined with how the suit makes his voice more muffled and echoing (can't be heard in fights means no quips, sorry), Danny is basically bearly seen, silent, all spooky and glowy in public. A cryptid.
That means when someone sees him they are more concerned about what they are even seeing and not the spicy details like who created the suit.
And even when people start to talk, there are so many theories based on single encounters that almost noone is even close to the truth.
Right after Danny looses the suit, he is overcharged, overpowered and totally not prepared.
As he stabilizes he has to relearn how to fight and for a bit he's basically a glass cannon. Good thing he has friends that can help.
I wonder what habits are going to stay tho 👀