The FF have a great, dramatic origin. Reed has all these ideas but can’t get any funding, so he sneaks into NASA and steals a rocket to go into space with his pals. And screws them up. That’s a quality first 30 minutes.
That said I think the FF works as a family or space faring adventurers. Marvel’s Lost in Space. And if you have an origin you have no FF kids, and the kids make the property sing. Plus I’d like a Reed that’s super smart through experience as well as intelligence - a human being who knows exactly what’s going on in the universe beyond Thanos, the Guardians and so on.
I’d assume Doom will be the kind of character who pirates Stark tech to make his own Iron Man suit.