Well, there is ancient life shaping tech - the halfings had it during the Blue Age, but like most things, it was lost. The glories of the past were burnt to ash by war and the naked pursuit of power.
As for the rest, it’d be hard to properly fit it in Dark Sun IMO. Highly advanced moon civilizations? Maybe, if they wanted nothing to do with Athas, and had no concerns about the state of the planet, walled off gardens that saw only to their own concerns. Outsiders are killed or mind wiped and returned. They don’t want greedy eyes turned their way, unless they’re just trying to wipe everyone out.
I’d have to say no to Orcus outright. Demons and other outsiders have no place in Dark Sun IMO. There are no gods or outer planes - just the Grey and the Black.
There would be psionically empowered items, but it wouldn’t be like Eberron, where they are a part of daily life and guilds exist to maintain them in cities. Dark Sun is resource pour, and you can’t really have a Bronze Age setting when it’s Fantasy Industrialized. That would fit better in something along the lines of Arcanum IMHO.
Crazy inventors aren’t generally a thing unless what they make is really useful, and then they’ll be snapped up by a powerful patron and monopolized or killed. None of the powers that be in the Tablelands have any interest in sharing power or improving the lives of their citizens unless there’s a direct benefit to them, except for Oronus.
I’d keep out most of the Spelljammer material. Rare visits are OK, but it’s the same problem as allowing easy planar travel - if it’s not hard to leave Athas, why would anyone stay? A Spelljammer craft is more likely to get swarmed and destroyed or, less likely, taken over.
During the Green Age, the sky is the limit, but I don’t think that’d affect planar travel. The Green Age could easily have psi-tech societies - it was was a gentler, more prosperous time.