He can go invisible, but it's not a great power. If he's on a wall and no one knows he's there, he's probably going to avoid detection for awhile unless someone gets too close. In one of his earlier comics, he was being chased by the police. He turned invisible, and hugged against a wall a few stories up. It kept him hidden until a search light happened to move right over him, and the cops immediately spotted him. Basically it's a decent spying/infiltration tool, but not much else.
No, Hellcat and Squirrel Girl's problems are that nothing fucking happens,, and if something does, the main characters don't even do the fighting. A story about some well-intentioned teenage superheroes could be fantastic. If you can't imagine a short story about Miles and Miss Marvel stowing away on a plane to some foreign country to help and can't afford to get there on their own wallet, you're dumb.
Plus, there's plenty of opportunities for them to actually fight big level shit. Who's to say that the latest threat the Avengers fought wasn't actually a manufactured villain, for someone to move in on a wartorn area and set it up as their base of operations once the big league heroes had fucked off, assuming the threat was dealt with?
God dammit, user. You weren't supposed to turn that into an actually really cool idea. That actually sounds amazing.
I could imagine the plot working as a sideline to a huge universe event. My thoughts: Supervilains all band together a la Old Man Logan. Except it's not a one night thing, and it turns into a huge war inside of America. Captain America dies during the initial onslaught, and there are a bunch of different factions of superheroes with their own ideas on how to fight the supervillain conglomerate. So Cap's shield becomes a symbolic rallying point, and whoever gets it will basically become the leader of all the superheroes. Until someone gets Captain's shield, the war can't end because the superheroes are so fractured the can't make a decisive strike, and no one is banding together because they aren't really losing the war, it's just stuck in a stalemate.
Meanwhile we have Miss Marvel who was entrusted with Cap's shield as he died, with the promise that she would find a proper wielder for it. She knows if she gave it to the next person she ran across, they could win the war immediately, but she can't bring herself to betray Captain's trust, and wouldn't be able to live with herself if the shield ended up with someone like The Punisher.