Well, one way it could develop is that Izuku starts to incorporate Iron Man's technology - like his repulsor tech - into his hero gear. He might study Tony Stark's engineering skills and use that knowledge to upgrade his costume, adding things like enhanced propulsion or better defense mechanisms. Maybe he also adopts Iron Man's confidence and quick - wittedness in battle, becoming a more strategic hero.
One possible plot could be that Izuku, with his determination and unique quirk, somehow gets transported to the Marvel universe. There, he meets Iron Man. Iron Man, being the genius he is, is initially skeptical of Izuku but soon realizes his potential. They might team up to fight a common enemy, perhaps a villain who has technology - based powers that combine aspects of both their worlds.
Maybe it's Obadiah Stane. He's jealous of Iron Man's success and with Izuku in the picture, he sees an opportunity to get rid of Iron Man once and for all. He could also see Izuku's quirk as something he can use to his advantage, so he tries to capture Izuku and use his power against Iron Man.
It might have a similar color scheme to Iron Man's suit, like red and gold. There could be a glowing arc - reactor - like device on his chest that powers his suit. The suit would probably have boosters on the feet and hands for flight and enhanced punches.
In this fanfiction, Izuku could be inspired by Batman's lack of superpowers but still being a formidable hero. He may start training in more martial arts and stealth techniques, similar to Batman. And he could even create his own set of gadgets, like grappling hooks and smoke bombs, to aid him in combat and rescue missions.
Well, if Peter Parker becomes an Iron Man fan, it could lead to some interesting developments. He might be inspired by Iron Man's tech and try to incorporate some of those ideas into his own Spider - Man gear. For example, he could work on making his web - shooters more advanced, like adding some of Iron Man's repulsor technology to them.
The Joker could be a great villain. Imagine if the Joker - like character emerged in the My Hero Academia world. Izuku, with his new Batman - inspired skills, would have to use his wits to outsmart this chaotic and unpredictable foe.
Perhaps a new villain could emerge who specifically targets Izuku because of her new gender identity. This villain might see her as a symbol of change in the hero society that they don't want to happen. So they constantly attack her and try to break her spirit, thinking that if they can stop her, they can halt the progress of female heroes in general.
One possible plotline could be Izuku adjusting to her new gender identity while still trying to pursue her dream of being a hero. She might face different challenges and prejudices in a male - dominated hero world as a girl. For example, some male characters might underestimate her at first but she proves them wrong with her skills and determination.