why, they ret-conned several gen 1 pokemon into fairys already, and given what was changed moonstones now have a strong connection to fairys.
idk I don't think it's plausible at all but that's just me. I do agree that fairy types seem to have an affinity to the moon for some reason but idk. that would just bug me because for the previous 17 years a moon stone wouldn't do **** to eevee as if nobody has ever tried it before lol. the closest thing to that suggestion I can think of that has actually happened is from gen 3 to 4 where tangela, piloswine and yanma all evolved by learning ancientpower which they could do since gen 3 to no avail. but idk this is a 6 generation difference lol
sorry that's all off topic actually but for now I'll stick to my theory that if Amie is unavailable in ORAS (which I don't see it happening since it's based on a French pun and this is no longer Kalos) then sylveon will just have to be traded over.
I don't know if this means anything but sootopolis city is based off the Greek island of Santorini also known as Thera. if that's anything to go by, then maybe that's sort of a reason why they went with omega and alpha because in all honesty I don't get why the Greek add-ons, but I'm excited to find out regardless.
also good to note sootopolis city is where the titans originally clashed.