Marvel would have had no legal ground to stand on. They licenses the characters out to FOX, so they had no say in their use. Marvel didn't give those up in a way a JK Rowling did. They made that contract when they were desperate for money.
First off, any license is going to have restrictions. No matter how desperate they were, lawyers would have been involved and language would have been included that would prevent, for example, Johnny being portrayed as a pedophile or something else that would damage the characters and brand.
Secondly, when people have asked "How can you prevent the Roger Corman situation from happening again?" People in the know (I believe Avi Arad was at least one who commentd) told us that a quality clause was included when the rights were transferred from Constantin to Fox.
We don't know the exact wording, but conveniently, we do have a specific quality clause from a contract that would have been written right around the same time likely by some of the same lawyers for the theme park rights:
http://www.insideuniversal.net/2016...ct-what-rights-does-universal-and-disney-own/
That contract states:
Each THE MARVEL UNIVERSE shall be operated and maintained in a first class manner consistent with the highest standards of the theme park industry and shall be deemed open only when operated in such manner (subject to temporary closures for force majeure events as described in the prior paragraph).
At such time as any THE MARVEL UNIVERSE is no longer open at a particular Universal Theme Park, all exclusivity and marketing rights acquired by MCA as a result of the opening of such THE MARVEL UNIVERSE at such Universal Theme Park, as set forth in Section IV below, shall terminate and this Agreement shall thereafter be construed as if the notice of intent to open THE MARVEL UNIVERSE had not been given by MCA.
With that specific statement in mind, I have speculated that the language in the film contract could look something like:
Each FANTASTIC FOUR FILM shall be produced and distributed in a first class manner consistent with the highest standards of the film industry. If a FANTASTIC FOUR FILM is produced that is not consistent with that standard all exclusivity and marketing rights acquired by Fox as a result of releasing FANTASTIC FOUR FILMS, as set forth in Section IV below, shall terminate and this Agreement shall thereafter be construed as if the notice of intent to allow production of FANTASTIC FOUR FILMS had not been given by MCA.
That is clearly intentionally vague language that would be a double-edged sword in court. It would be hard to point to one specific thing as a clear violation, but a skilled lawyer should be able to use that language and Fant4stic and make a case.
Remember all the rumors about Josh Trank both before and during production? Those are only rumors at this point, but Disney lawyers would have the power to subpoena people who had been involved and ask specific questions like: "Were you considering replacing Josh Trank? Why didn't you replace him? When there were clearly problems during production, why did you continue without bringing in a different, experienced director?"
We've heard about ugliness on set with things like Trank hiding out and not talking to anyone and leaving the crew to film without him along with things like him (apparently thinking he was Hitchcock) intentionally abusing Kate Mara so she would feel "invisible". And the attitude and tweets from the cast after the film had been released seemed to indicate there was some ugliness and bad blood. Swear them in, get them on the stand and find out what really happened.
No matter what the specific wording of the contract is, I'm certain a qualified lawyer could make a strong case that Fant4stic was an inexcusable misuse of the license that damaged the characters OWNED by Marvel/Disney.