Maybe, but it's also far less appropriate than saying "they would ordinary be excluded because Athas lacks a connection to the feywild, but here's a modified version that fits with the themes and character of the setting." If you're talking about allowing a single player to make a single Eladrin PC, you can make a virtually infinite number of excuses for how that character arrived on Athas without originating there because of all the magic in all the worlds of D&D (as I said earlier, it's just as easy as saying a character from any other Palladium game was drawn through a portal into RIFTS Earth).
That's a cop out. If I'm playing an Athas campaign, I want Athasian PCs. I don't want "Bob, who came from Oerth" hanging out. I want to use Eladrin NPCs, tell stories tied to the Eladrin, and have multiple Eladrin PCs. I don't want "planeswalker eladrin ends up a Athas". There are far better ways to integrate a new race than have every one of them be off-worlders.
Sorry, but I have to call BS. There is no "hardline no" as it relates to the races of individual characters, for reasons I already mentioned. An orc PC fits into Krynn just as well as an Eladrin PC does to Athas. However, having a section that explains "this is why they were excluded, here is a modified version that fits with the setting, and here are ideas for bringing in PCs of that race from other settings" is inclusive, thorough, and educates people new to a setting about the intended character and feel of the setting while giving DMs tools to ignore that intent if they so choose.
You're fighting on both sides of the argument now?
What makes Dragonlance unique?
There are no orcs. But heres how to import a bunch of orcs from Faerun.
As soon as the 2e PDFs start including mechanical update appendices for every edition that comes after, I'll agree with you on that.
Sure. A 5e update, and then the 2e PDFs to show the world "as it was". Win-win.
"Arthaus Ravenloft?" I've never head of a product called that. A quick Google search appears to indicate that you're talking about the 3e Ravenloft books. If so, I liked those books. I liked what they did with the dark lords and land masses changing (I didn't have a problem with Soth losing his domain or with that Necropolis domain nestled within Darkon), and I liked what they did with the Weathermay twins taking on Van Richten's mantle in his absence. Notably, all of those things are in keeping with the tone and character of Ravenloft.
I was. However, isn't ironic to comment how you like the 3e changes to Ravenloft when it introduced Calibans (Ravenloft half-orcs) and found places for paladins, druids, bards, barbarians, monks, and sorcerers in the setting? Not just "ported over and stuck" but home-grown versions? By your Dark Sun example, The Ravenloft PHB should only have had Fighters, Rangers, Rogues, Wizards, Clerics, and then a section on "how to import other classes from other settings".
It shows what I've been on about, you CAN expand the setting's options while keeping true to its spirit.
That's making things a bit personal don't you think? I have no problem with changes, I just want them to be in keeping with the feeling, the tone, and the character originally intended for the settings. You can play it as jumpscare slasher "horror," but Ravenloft should always be designed primarily with a gothic horror feel in mind because that is the identity of the setting.
I didn't mean to direct it at you, I was directing it at the setting. A setting needs to grow and evolve. It Dark Sun doesn't allow more options that it did in 2e, its not worth converting. There is nothing about gothic horror that precludes monks or elves. There is nothing about sword-and-sandals that precludes warlocks and dragonborn. There is nothing about romantic fantasy that precludes sorcerers and half-orcs. The tone of the world isn't defined by what is cut out of the PHB.