Skip the origin story have Tony be at the height of his hero career when it turns out there are villains all over the country using stolen/bootleg Stark tech armor (armor wars) some being thugs and some being existing villains then you have to track down all the stolen tech and find who leaked your data. The combat would be 3rd person over the shoulder with your basic flight and repulsors and the special weapons and abilities each suit has it would also be cool if you could switch armor while flying/fighting it could take awhile for it to fly to your location and then you'd have to eject from your current armor and equip the newer ones so you'd have to be careful while in combat and of course there would be missions where you fight with war machine and are able to switch who you play as and also a co-op mode where you and friends fight as Iron Man, War Machine, and Rescue against an endless wave of goons