Originally Posted by Spider-Fan
They have film rights to the Fantastic Four characters plus the villains and Galactus/Silver Surfer. This includes their ultimate versions. No matter what is different between 616 Reed and Ultimate Reed, one thing is the same: It is Reed under copyrights. There is no distinction. That'd be like saying you own the rights to Spider-Man, except Web of Spider-Man. Such a rule doesn't exist.
The only case of something like what you're outlining existing is the rights to Superboy not being owned by DC. But, the Seigal/Shuster estates won that in a lawsuit. Such a lawsuit has not come from FOX/Marvel in regard to FF film rights, and if it ever did, I highly doubt they'd ever seperate them.
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.