Essentially, Spider-Man 4 could have Peter Parker take another character’s place in the dynamic with the Iron Man AI. In Marvel Comics, Riri Williams, aka Ironheart, was the one who had a meaningful connection to Iron Man. After scouting her as a potential talent, Tony Stark created a backup of himself just in case he ever came to pass, and after his death, the AI version of the Marvel hero was sent to Riri. Under his guidance, Riri became Ironheart and went on to save a lot of people. In the MCU, Spider-Man would make sense instead of Ironheart.
Despite being an AI, Iron Man was still quite active. The AI version of Tony Stark could control his Iron Man armors, which meant that the hero could still help out others in the field even if a physical body was missing. The AI Tony Stark was a reconstruction of his consciousness, which led to the character developing identity issues due to not having a body. That could provide Downey Jr. with a fresh and interesting arc in his possible MCU return, something that could go in hand with the expected darker and more intimate tone of Spider-Man 4.
