Yeah, maybe an airline can say to the airport/CBP "we'll pay to rent a lounge/corridor/gates at this airport in this terminal for a sterile transit option between our flights or our partners' flights because some passengers want that" and maybe the airport/CBP can approve the proposal. (Maybe non-U.S. passport holders will still require an ESTA, but not a CBP examination?)

I think the specific option at LAX was post-2001, but you had to be on a specific pair of flights to take advantage of it. (I didn't do it, I just read about it on FlyerTalk and forgot the details.)