Most people don't give a shit about fantastic four.
If anything just bring Skrull back to rep them. No one wants 4
Slots wasted on B tier characters. Their books don't sell well, their movies suck and the character designs are lame.
Anecdotal, but no one I've ever known or spoken with has ever mentioned F4 in any way shape or form. It's not even negative things sAid, just nothing. They are culturally bankrupt as an IP.
Game will be better with out them.
What wil hurt is wolverine and Magneto missing because they are such legacy characters but wolverine move set/ archetype can very easily be given to like 3 or 4 different characters, Blavk Panther being the most obvious choice.
Magneto could likely be replaced by Vison. Flight, projectiles, quick movements, ect. But really I think he could be even more interesting than Mags in the end due to phasing thru things.
Storm can easily be replaced by Scarlet Witch if they really wanted to. Or a host of other female characters in the Marvel-verse. Captain Marvel, Emma Frost, the Ancient One, Song Bird... Plenty of choices.
As mentioned by myself and others Sentienl is an easy replacement with the Destroyer from Thor 1, or the Hulk Buster armor (why not both?)
SpiderGwen could be cool potentially- I really like her design but it might be difficult to differentiate her from Spider-Man , lots of web moves and whatnot, could be a shoto clone type situation.