I have an idea.
The Future Foundation Returns: Alex Power has stumbled out in front of the Yancy Street heavily injured. When the F4 heal him, Alex recalls their journey to find the Molecule Man. Unfortunately, they were opposed by creatures from the Realm of the Beyonders. See, when Doom killed the Beyonders, another species has taken hold at the top of the evolutionary food chain in their dimension. If Owen Reese returns, that means that would have a Beyonder and therefore a threat to their power. Since Owen is dead and scattered, they want to keep them that way. They took each member of the Future Foundation for good leverage.
Reed puts his children and a newly reassembled Power Pack in charge of rescuing the Future Foundation while the Fantastic Four deal with the beings from Wild Space.
The Fantastic Four move to turn these beings against each other since they know overpowering them isn't an option without Franklin. To do so, they need to physically go into the realm of the Beyonders and study the cultures of that world. Ready yourself for some really trippy imagery that pay homage to Ditko and Kirby.
Meanwhile Franklin goes on an angst fest over how his powers are now an Mana bar (cause someone had to write an explanation about how those mutant powers worked). They rescue a member in a unique environment (world corroded in dark matter, frozen maze, astral plane, world where gravity doesn't exist etc.)