I'm certainly glad NONE of you work for WotC.
I don't know, I kind of get the idea of adding things to the setting if they fit the setting.
For example, from the little I played of Dark Sun... well, I think we ignored 90% of the point of the setting, but from what I've heard the Desert and the idea of Elemental powers is a big deal. Doesn't the concept of the Storm Herald Barbarian with the path of the Desert fit that kind of setting like a glove?
I don't care if barbarians never existed in Athas before, the idea of a tribal nomad who is able to channel the might of the desert to destroy his foes, in a world where the might of the desert is a big deal, makes perfect sense to me. However, the other two sections of the Storm Herald, especially the cold tundra version, make incredibly little sense. I don't even think they have snow-capped mountains in Athas so having that Barbarian in a game would be a tough sell, I don't think I could accept it.
So, the idea IMO isn't "Can I find a place for my Polar Bear Divine Chanter of Kord character in Athas" but it is asking, are there new ideas and things in the game that make sense to appear in Athas? Are there classes or races that didn't exist in an older edition that fit the setting very well with a minor change or two?
Also, we could look towards potential re-works of ideas, I only played 4e Dark Sun, but the ability to choose whether you preserve or defile with each casting was kind of cool. I was a goody-two shoes so I never did, but I had that option. That seems like a good thing to keep, instead of making a whole new subclass to represent each side of the coin and only using those two.
Orcs in Kyrnn seem to be a big deal to some people (I thought they were there but its been too long since I read the novels) but if it truly messes with the setting that much, fine, leave them out, but I wouldn't leave out Tritons from Dragon Lance, because they seem like they'd make a good interpretation of the Sea Elves (also, I really don't want to see 20 different elf subraces, just, no please no)
I just think we shouldn't limit ourselves if we don't need to. Just because every setting has Humans, Dwarves, Elves and Halflings doesn't mean they are all the exact same setting, very few settings are fully or even partially defined by the races or classes available, and environment, cosmology, and types of threats are a bigger indicator of a setting and what it is meant to be like than what kind of characters are at the table.