There are actually several precursor races in Star Drive — one is the Stoneburners, the others are the Glassmakers, Those who Think, and the Starweavers. I think you might be able to rewrite the Primordial War as the conflict of these forces, and see the Stoneburners as the pregenitors of the Ilithids, beholders, neh-thaluggu, other mythos races, kreen, neogi, and aboleth. I honestly didn’t like the fact that 4th edition added its cosmology to Dark Sun – I think it should be its own thing. I honestly think the 2e era was much better at fluff than anything that came after it. That’s why I’d prefer to work on the Spelljamming and Stardrive connections rather than focus on 4e Dark Sun (I also don’t like that 4e got rid of the Kreen empire as a real thing). There are some other Star Drive races, like the psionic Fraal, that would work as occasional visitors or players in the history of Dark Sun. I could imagine an underground lair of Thaal (the evil Fraal) who were left by their masters and are sleeping in bioorganic pods.
I don’t remember if much was detailed about Stoneburner tech besides that it was bioorganic, but I’ve thought of it as similar to the black oil from X files and the engineer black oil from the Alien franchise – as well as somehow connected to the tenebrion seeds of Arcana Evolved and idea from Lynn that magma is somehow connected with draconic magic. All these sorts of black/superheated, vaguely organic concepts could somehow go back to the Stoneburners.
Another idea – what if the Anguiliians, Psurlons, and Ixitxachitls were all connected to the Stoneburner race, and there were silt-breathing variants that evolved that still have extant realms deep in the open silt between the continents.
I personally think it’d be more interesting to trace all these different aberrations to another, more-frightening precursor psionic race that was squid-like, but the size of krakens and able to travel with worm holes or just fly through space. There might be some remains of them somewhere in the deepest silt or underground – sort of like the primordial concept in 4e, but its own lore.
Here are some other ideas – what if we expanded, on the other continents, the concept of alternative energy advanced beings – like an avangion who uses Cerulean energy, or a ‘dragon’ that draws on one of the paraelemental planes? Another area of the world could be some advanced being/elemental lord city states that are fighting an alliance of paraelemental dragons. I know some didn’t like the alternative energy sources, but I think you could fix the issues if you made each corruptive or dangerous in some fashion – use of shadow magic has the risk of your shadow coming alive and eating you, cerulean energy has a change of trapping you like Titian and sucking your mind into the storm – something like the Storm from Accordlands – the grey can slowly turn you into an undead, etc.