I could dig it if Dark Sun leaned heavier into its Barsoom inspirations. Kreen dominating beyond the crater would certainly have a green martians roaming dead sea bottoms vibe. If I'm being honest, I like that better than the Crimson Savannah.The existence of a giant crater-like ring could at the minimum imply the existence of the astronomical phenomena that make craters. But more than that, it is a nod towards the sorts of sword and planet fiction that have inspired Dark Sun. I’m thinking of Barsoom.
It doesn’t have to be a published reason for why “civilizations” are clustered inside the crater, there could be any number of options open to DMs, like after the Cleansing Wars we’re over the Sorcerer Monarchs settled within the crater to “start over”, but outside the crater the rhul thaun halflings and their kreen and other desert survivors dominate. Or, the Cleansing Wars destroyed the planet but the Sorcerer Monarchs did not win and had to retreat within the protective mountains of the crater.
Wait, really? Where does that crop up?We have to remember the time travel was oficially canon in DS, and this means the possibilities of alternate timelines where you can customize to your linking.
Perhaps not, I can only speak for myself.I have to wonder, though--do Dark Sun fans want to deal with armies and mass battles? From what I've seen, the draws appear to be the Mad Max-y post-apocalypse-ness plus biotech and psionics and mutants and stuff like that, illustrated (by Brom, of course) in a planetary romance style.
I'm thinking of the intensified conflict more as background context for PCs to get involved in at higher levels if they want. It'd be a way to foreground defiling and the vehicle driven parts of the mad-max milieu, as well as making the world the PCs live in dynamic. The reason I like it is that it would allow Dark Sun civilizations to have the scale that lots of the setting materials want for it to have. The too big armies listed in the 1991 set, the unfeasibly large draft animals, the spectacular monumental buildings--at larger levels of social organization, those things make more sense.
But, in fairness, that's just one answer to the 'what would make new areas significantly different from the Tyr region' issue you posed. I would welcome other novel and interesting responses to that question.