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.
That's about as far from the standard power fantasy template as you can get, but if you want to keep breaking the mold, these are the kind of risks you have to take.
It's a heartbreaking tale, but it also works with Thor's motto in Ragnarok: "Why? Because that's what heroes do." Also, if Portman feels iffy about signing a contract for ten more Thor movies, she could just do one and have the ultimate serious actor's superhero role under her belt.
Related: 5 Marvel Superhero Teams We Should Be Giving Our Attention
There's A Good Batman Comedy Out There (Without Bruce Wayne)
In the history of Batman movies and TV shows, we've only gotten one that deviated from the formula of "Here's Bruce Wayne drop-kicking clowns." And even that one, the fantastic Batman Beyond, featured Bruce Wayne in a mentor role, yelling tactics at a goddamn teenager. And with Ben Affleck leaving, there's a real chance that we could take a character that needs a refresher and ... well, not give him that.
Instead, Warner Bros. could go the way of the comics and introduce Bruce Wayne's son Damian. See, Bruce's relationship with Talia al Ghul (Ra's al Ghul's heavily cleavaged daughter) results in a boy that she keeps secret from Bruce. Then, when Damian is a teen, she drops him into Bruce's lap, which is kinda hilariously villainous. As can be expected, Damian's pissed and violent, and he hates all of Batman's Robins, presumably because Bruce Wayne actually went to their baseball games.
In the comics after Batman "dies" at the hands of Darkseid, former Robin Dick Grayson dons the cape and cowl, and Damian becomes his Robin. Their dynamic is ridiculous and hilarious, which is much more interesting than the usual self-serious "You're not ready to be, um, in crime stuff" routine that Bruce has with his Robins. Does it bring a "wacky sitcom" atmosphere to the franchise? Maybe, but we haven't had a live-action Batman film with a proper joke in it since the Clinton administration.