Your picks for a new or substitute Fantastic Four roster

[Noek]

Ahura Boltagon

Lightspeed (Julie Power)

Mass Master (Jack Power)

Energizer (Katie Power)

One of the last Future Foundation kids leading the rest of Power Pack.

[Panic]

Doc Samson
Aurora
Chamber
Ms Marvel

[DurararaFTW]

Black Panther
Storm
Spider-Man
She-Hulk

[KOSLOX]

All New Fantastic Four:

Black Panther
Storm
Kymera
Azari

Keeps the family dynamic with a touch of Exiles.

[LordAllMIghty]

Namor
Black Panther
Storm
Human Torch (Jim Hammond)

I can go with this team. They even hit the elements (kinda) too like the originals.

[Conch22]

Go completely with the new school:

America Chavez.
Mosaic.
Ghost Rider (Robbie Reyes).
Ms.Marvel.

[SchismOfMadroces]

Black Panther
Storm
Crystal
Hercules

[Photon Torme]

Lessee

Prof Hulk
Moondragon
Songbird
Spiderman- Pete

[mr_crisp]

Blue Marvel

[Crimz]

Moon Girl - The brains
She-Hulk - The brawn (plus she was a member before)
Scarlet Witch - The power (plus I like the idea of magic on a science team)
Iceman - The elemental

Then I would incorporate the team into the Future Foundation when Reed and Sue return, so that the FF have a bigger roster than 4.

[Photon Torme]

Ironman
Brother Voo Doo
Jean Grey
Hulkling

[Thor-Ul]

Surprised no one had come with this:

Miles Morales
X-23
Amadeus Cho
Robbie Reyes.

[Marxtles]

I would retain the Family element of the Fantastic Four using the following family:
Dr Henry Pym (once they have fixed the whole "merged with Ultron situation)
the Wasp (Nadia - Pym's daughter)
the Vision (created from a Human Torch and Pym's "grandson")

the 4th member is tough for me to decide on...I am debating between:
Wonder Man (Vision's "brother" - also an engineer himself)
Human Torch (Jim Hammond - the Vision's "brother")
Ant-Man (Scott Lang)
Stinger (Cassie Lang - Pym's "niece")

With this line up, I would avoid super heroics completely and focus on discovery and science fiction style story telling. The action and adventure would come from the dangerous that come from exploration....like Star Trek.

[Photon Torme]

Namor
DragonMan
Shadowcat
Iceman

[Tiamatty]

Gotta go with Silk, Wolverine (Laura, natch), Ghost Rider (Robbie) and Hulk (Amadeus). The All-New New Fantastic Four. I'm really disappointed they didn't actually get a book.