Little pre-serum Stevie comes out of the vita ray machine as a super buff and incredibly rad Amazonian-like woman and all the men are like “what? A girl?!?!? That was so not meant to happen!” But Stevie just grins so fucking wide and says “Well I for one think that went perfectly because I am, yanno, actually a woman.”
Stunned silence and cricket chirps… then one of the military douches starts to speak but Stevie cuts him off: “-wanna fight me about it?” She warns, raising her huge fuck-off fists.
Eventually the Hydra agent shakes off his surprise and shit still goes down…
Cut to Cap’s USO tours which still take place but at first the show runners expect Stevie to hang off the arm of the (still-not-as-big-as-Stevie) actor playing an American soldier so she can raise moral as “Lady Liberty”, but Cap and the showgirls have something else planned and on stage at the first live performance the Hitler-punching, day-saving Captain America is born.
The crowd absolutely loves it so the show runners just decide to just continue with it. War bond sales boom and female war effort volunteers rise exponentially.
When Cap goes to save Bucky she takes Peggy with her because Cap might be all super-soldiery but Peggy is properly trained and has all the local and strategic knowledge. They are like the most bad-ass team ever and when Peggy joins the Howling Commandos full time, the Command are too chicken-shit scared of her and Cap to complain.
Because Cap now feels comfortable in her own body (and after a few “talks” with the USO girls) she becomes more forward and her and Peggy actually start dating and are a nauseatingly cute yet scary power couple. Bucky is ecstatic that his sister-from-another-mister is now able to show everyone how much of a bad-ass woman she is and is actually managing to talk to (let alone sleep with!) another girl. He’s also just a bit miffed that Stevie is now taller than he is.
Bucky still falls :( but instead of Cap going after Red Skull alone Peggy forces her way along too. This means that when Cap needs to sink the bomb Peggy refuses to leave her side and they go down together.
Of course Peggy also survives the 70 year deep freeze (due to the sheer awesomeness running through her veins/being too damn hot for cold and time to shut down/Stevie’s saving embrace/whatever floats your boat) and so we welcome both Stevie and Peggy to the 21st C!! People in the brave new world are like 1000% more awed to have these forerunners of women’s, gay, and trans rights walking amongst them than they were for MCU Steve alone. Plus I want Maria practically wetting herself and fangirling way harder than Coulson does.
(Also because of Peggy’s absence in the interim decades there are major world differences- SHIELD doesn’t exist/still runs as a rather inefficient SSR, Hydra hasn’t been keeping in the shadows and some shit has already gone down before our girls are defrosted, Tony has more issues having not grown up with Aunt Peggy… But I have too many ideas about potential AU histories to list here.)
But anyway basically we get Stevie and Peggy as hella rad vintage lesbian Avengers and they get to team up with Natasha during CA2:WS to kick ass, save Stevie’s bro, and massively intimidate poor Sam.