You're right. The Marvel char rosters should not be restricted to add those who appeared in MCU, means won't be related to movie right issues since previous announcement of early months this year.
To me, seems Wolvie, Deadpool & Doom are the only Fox movie owned Marvel characters to appear in this game for some reasons:
* Wolvie: Being the face of MvC series since Childrens of the Atoms. X-Men is the one found Capcom's Mahvel fighting game in the first place. Him appear unexpectedly as Wolvenom (his DLC costume) on Story Trailer 3 involving Mind Stone will received from fans a positive reviews
* Deadpool: Not only Spidey/Deadpool #20, also his Fox's duology films & his increasing popularity since his video game appearance in X-Men Legends II, his hilarious VAs & a seiyu (Za Warudo/The World), then even joining the Avengers. Him appeared in Mind Stone Story Trailer will also led the game's positive fan reviews for him representing X-Men's involvement
* Dr. Doom: Being an universal adversary of Iron Man (commonly, but also w/ Avengers) as well other than F4 + way more popular than titular four heroes themselves (though Thing, Johhny Storm (2nd Human Torch), Surfer, Galactus & Kl'rt (original Super Skrull) are also universal))