I'd love to see her played by someone like Marsai Martin (Diane from the TV series Black-ish). Maybe have her, Shuri from Black Panther, and Peter Parker create their own Gen-Z superhero group and save the world from dangerous baby boomers. Perhaps this could be the start of the Young Avengers? Or just a new sect of the existing Avengers. Either way, this is better than simply rebooting the whole thing a few years from now with some other "lovable asshole" type with a Tony Stark goatee.
Related: 5 Superheroes Who Should've Gotten Movies Before Ant-Man
Let Jane Foster Take Over As Thor (For At Least One Film)
Alright, hear me out, ladies. Yes Chris Hemsworth's Thor is a surprising delight, and I've enjoyed every topless second of him, but the MCU has put him through a LOT. His brother and his dad are gone (for now), so maybe let him retire when this phase of the MCU ends. He and Valkyrie can settle down in the wilds of Norway and take solace in each other's arms. They deserve it, goddammit!
Then they can reintroduce the audience to Natalie Portman's Jane Foster. Only this time she'll be Thor, and arguably a better Thor than Thor is.
In the comics, Jane is one of the only people besides Thor who can wield Mjolnir and become God(dess) of Thunder. But with her, it comes at a price: She's dying of cancer, and the magic of the hammer seems to counteract chemotherapy. This means that every time she transforms into Thor, she gets sicker when she transforms back. Jane is well aware of this, but because Thor is out of commission and the world needs a hero, she keeps doing it, even as it leads to her death.