I kinda think Carol needs to have been known on Earth for at least a few years before they can do Kamala. Though I suppose they could just tone down the "Carol Danvers fangirl" aspect and focus more on her being a general superhero fangirl.
I'm... vaguely aware of her existence. Is she really more popular than Shang-Chi?
That would be cool, but I have my doubts on whether the MCU is ready to go full-on self-parody.
Questionable whether they have the rights, what with the Sony/Disney deal being up in the air.
The comics character or the MCU one? I very much doubt comics Valkyrie is more popular than Shang-Chi. MCU Valkyrie, yes.
Again, I can't imagine either of these characters being more popular than Shang-Chi.
And something I neglected to mention in my earlier post is that Craig listed Shang Chi being "niche" as a point against, but I'd argue it's a point for. Most if not all of the MCU franchises occupy a specific niche, something that sets them aside from the others. Marvel clearly has a formula, of course, but each franchise tweaks that formula in a different way. A Shang-Chi movie that combines the MCU formula with classic kung-fu movie tropes is right in their wheelhouse. It's less clear what hook you'd use for Tigra or Spider-Woman that would make them not just another super-hero movie.