We have all talked about it, but it has been done. Chip Zdarsky has written a nifty comic mini-series which details what would happen in Marvel characters didn't maintain their same age in a "sliding time scale". As such, the series details, "On this Earth, many Marvel heroes such as Spider-Man began their career at the time they were first published in comics, and are unaffected by the Sliding Timescale. Additionally, one of the major divergent events in this world is Tony Stark's decision to be more involved with the Vietnam War as Iron Man, which escalated tensions between the US and the Soviet Union and led not only to an extended Vietnam War, but a war in 1984 where nuclear missiles destroyed Allentown, Pennsylvania while many US superheroes disappeared to Battleworld. This War was won by the US at some undetermined time before 1995...."
See: https://marvel.fandom.com/wiki/Earth-2447
See: https://marvel.fandom.com/wiki/Earth-2447