Yeah, to this day, the close-up of Black Widow’s bullet wound on her stomach is the only bone that has been thrown to us. While the men always appear shirtless on screen once per movie, the women never take their clothes off.
On the subject of swimsuits, I often joke that as an Easter egg, Marvel should have a pool scene where Brie Larson should wear one of Miss Marvel’s past costumes as her swimwear.
As for female characters best suited for a beach or pool scene, they could always introduce Wave, who is pretty much a Filipino and female version of Namor, the Sub-Mariner.
They would just have to go with a comic book accurate version of her costume. Chances are, Vanessa Hudgens would play the role. She’s never shy about showing skin, and she proved with “Bad Boys For Life” that she can whip herself into action heroine shape if need be.