To clarify: I was specifically commenting on what was mentioned in your original post
Since they were put next to each other, I assumed they were related. I’m now assuming that these were two separate questions, being: “Is it legal?” and “Do you like the systems/physics in the mod?”.
Normal trademark/copyright law still applies then. Copying the assets. The operator select screen would be a prime example of infringement, and characters would be referenced as being copies too (infringing on likeness).
EDIT: Legally, it’d be something that someone could pursue, and the creators probably know that. They’re probably just not worried about it, until it actually happens (if it happens). But that’s me making assumptions about their point of view.
It’s interesting to see a fan-made recreation of it but unless they got permission then Ubisoft could take legal action against it if they wanted to. I’m hoping that operator select screen was just Photoshop and not what’d actually be used. If they incorporate that specific image in it then they’d definitely be setting themselves up in a bad position.