[FaeLenx]

I think the only major problem is that nobody really considered any lore to write up for Papillion or naga that would make them more specific to Korvara. There is of course a reason for any race to exist or to not exist, but everyone just kinda figured 'well they're just kinda around. I guess.' Reasonably, in the planning stages of Korvara, someone could have figured that all out.

I don't see any particular reason to include Zeran or Mechanations besides a few fun mechanics there. There are plenty of races you can play that have horns.

For Mechanation, I can see so many reasons not to. Without solid lore for where they come from, they're just a bit weird to play. Where Papillion could at least be handwaved to be from any source of corruption that other corrupted races get changed by or one other odd source specifically near Korvara, Mechanations require a specific item and a lot of development of said item to exist. More importantly, it would require a lot of the mysteries still included in Sigrogana to be divulged for them to be in the much more player driven Korvaran lorescape since these are the same worlds.

For Zeran, their powers don't really thematically work unless they have something to be proud about. They'd be doubly odd on Korvara, and if there's ever a bridge between the two settings it would be incredibly bizarre for Sigroganan Zeran to learn that people who looked just like them exhibited the exact same powers as them despite not having that connection.

Elves work because they work just as much here as they do on Sigrogana.

Liches and Vampires don't work because they don't fit the theme of a consequence driven atmosphere.

Dullahan don't work because we really don't need everyone flexing a ridiculous Dullahan build in PVP every time there's a war. They were made to be fun in an environment without implicit competition. With that competition now involved, they would just not be fun.

I like mechanation and Zeran as much as the next player, but I don't think they're necessary. Also, the 'crashed a ship on Korvara' pursuit is the opposite of what a lot of people wanted early off. That kind of sudden injection of Sigrogana lore into Korvara would neuter a lot of current conflicts and change a lot, especially if people started to conveniently take to the existence of actual, real gods with tangible benefits to their worship.