Let's go down the rabbit hole of fantasy casting. Not fantasy as in wizards, flaming swords, and panpipes that cause people to walk. Fantasy like "Wouldn't it be cool if ________ played ______?" Pick anything. Want to see Katherine Hepburn in Garden State? Weird, but sure, why not? Patrick Warburton as Ebenezer Scrooge? I've seen worse.
Leslie Knope Amy Poehler as the President on West Wing? Anything is possible. Craig Ferguson as the Master on Doctor Who? WHO DOESN'T?!
I mean, you can certainly choose someone for a SF/F role. Quasi Hatrack asked the O-Deck what people wanted to see Katee Sackoff star in besides a Captain Marvel movie. I said as Karen Murphy in an actually good version of Dresden Files.
My offering: I would love to see Aubrey Plaza play Deathbird in a Shi'ar movie.