If your film is to be perfectly realistic, then a NASA-like design makes sense- but then the anthropomorphic aliens and the floating islands don’t make sense, because they’re not realistic.
If you want a realistic sci-fi film, have realistic (non-anthropomorphic) aliens and worlds.
If you want to admit these unrealistic elements, give your humans more fanciful looking technology- it puts the film in the realm of space opera/fantasy, where our laws of nature don’t necessarily apply.
Personally, I’ve seen a hell of a lot of space opera on screen, and very little hard sci-fi. I’d like to see some of the latter for a change.
By the way, solar sails are a real-world concept. They’ve been exaggerated in some sci-fi, and may never be practical, but the physics is there.
I’m pretty sure the native Na’vi were the ones wearing the tribal outfits- and they’re anatomically identical to the avatars, as near as I could tell.
Is this a space fantasy or a hard science fiction film? The realistic human technology, and the unrealistic environment and aliens are at odds with each other. That’s my problem.
I’m not sure the market for hard sci-fi would be so small- science fiction has become immensely popular and profitable. And hard Sci-Fi isn’t necessarily ABOUT the science, it just respects it. Those who don’t know the science wouldn’t necessarily know the difference.
If it’s pure fantasy, then it’s “Space Magic” and you don’t need to explain it. If it’s SCIENCE fiction, you’ve got nothing. Superconductors repel from magnetic fields- it would have to be Pandora itself (not its parent planet) that had a strong magnetic field to cause superconducting islands to float. But you run right into the law of unintended consequences. To levitate massive islands like that, the magnetic field would have to be so intense as to dramatically effect any ferrous metal on the planet. Any machinery would be dragged toward the nearest magnetic pole- I suspect it would also rip spacecraft right out of orbit.