Mind of tempest
(he/him)advocate for 5e psionics
make sure all the rules are more or less the same or at least do not change the basic ground the PHB laid out.I think they could make it work if each was part of a 'complete' set - i.e. you buy the Dark Sun Box Set, you get the Dark Sun phb and mm and dmg, one 1-20 campaign, and some minis and a map or two. The trick is to assume that WotC will never expand on this - that's the Dark Sun product. After that's out - they're done making official Dark Sun products. If you want to homebrew stuff for it, pull in stuff from other products, by 3pp, that's all on you. Like Legos, they're yours to play with however you want and can be combined with any other product line, as you see fit, but the company isn't going to get into that. Just do your thing.
The next product from that team is the Official Spelljammer Box Set. (Ravenloft would come before Dark Sun, but I digress).
Of course they'd need to sell the Dark Sun PHB as a separate product, and might as well license a line of player minis, but the main thing is to treat each as a singular product so they're not splitting the brand.
honestly, I would buy this assuming I got a psion out of it.
I would also put out big consolidation books if the line gets big like the reprint of the artificer but more cohesive for different things like a big part two to the default dmg and phb, a part two but not a 2.0.That I think would have to be the trick; WotC's Presents: Dark Sun The RPG could work as a one and done product, but it would begin to cannibalize if they released multiple supplements for it. And multiply that by every setting you want them to support. TSRs biggest sin was trying to sell you supplements that only worked with certain other supplements.