So here's a few questions that've been bothering me:
If the RDA can just back up and resurrect Quaritch (or whatever Lang's character was named) literally from the dead as a Na'vi avatar, why the hell is Sully even in these films? Surely they'd have backed up his dead brother and everyone else who was actually a part of the Avatar program, if they could and did back up some random colonel's dead brain. That has to be cheaper than literally flying a cripple and his wheelchair four-light-years through space, and a hell of a lot faster too. Hell, why even bother sending the actual humans if you can just upload them permanently into new bodies; copy their minds, send them digitally through space on a communication laser to be input into their bodies on Pandora and skip the costs and time of shipping their physical body at all.
And on the subject of time; since it takes at least four solid years to even get to Pandora at nearly light-speed, that means Sully's brother died, Earth finds out about it four years later when the comms arrive, and Sully gets sent on the ship to arrive at Pandora another four years later. So what did they do with his brother's avatar body for the decade it was dormant? Was it just floating in a tank the whole time? Were humans really on Pandora in avatars talking with the Na'vi for most of a decade? The timing of the first film has bothered me since the first time I saw it. It all feels like they just arrived, just started communicating with the director's barely concealed cat-girl fetish people, and nothing feels like they've been doing this for years with no progress. Half the Na'vi kids they were teaching should've already grown into adults helping to integrate the humans with their tribespeople by that point.
Maybe all this is explained in the films, I don't really remember them well enough and don't care enough to waste my life actually re-watching the first or ever seeing the second. But I don't think the film ever went into the world-building enough to explain anything like how the Avatar program actually worked.