Everything that really distinguishes Fantastic Four from Ultimate Fantastic Four, apart from the age difference, is in the context they're placed in, and that context is largely made of characters and concepts Fox don't have. I'm pretty sure I've seen Feige, when questioned about FF, indicate that there's a list of every character Fox can exploit under the terms of their deal. If they had every character that was introduced as a FF villain or part of the FF supporting cast, they'd have Black Panther, they'd have the Skrulls, they'd have the Inhumans. The only characters we really know Fox can use are the ones they either used already or mentioned as possibilities for Fantastic Four 3. I think that list looks like:
Mr. Fantastic, Invisible Woman, Human Torch, The Thing, Doctor Doom, Galactus, Silver Surfer, Alicia Masters, Puppetmaster, probably the Mole Man.
That may be most of the list. Maybe they have a few others (Dragon Man? Diablo?)
It sounds like they don't have a lot of room to move around in with these characters.