Something about the new Ascian lore

[Seraphor]

That's my take, too. A lot of people are still treating Hydaelyn as if she is a deity - but she is not, she's a Primal and our character is a Primal slayer.

It'd be rather disappointing to me if it turns out that Hydaelyn is conveniently the exception to the rule and needs to stick around but Zodiark is bad news and needs to go. I want a bolder, more nuanced story than that.

Light=evil and Darkness=good is just as derivative these days. I'd find it just as disappointing.
The story can be nuanced without being a cliche.

So far, the vast majority of primals have been summoned due to Ascian teachings, meaning that most primals we've faced are at least somewhat related to Zodiark's summoning, sharing the tempering effects and high aether costs.

Hydaelyn could represent an entirely different school of summoning that we haven't really seen anywhere else.

And again, take note of the methods of summoning.
Zodiark required the sacrifice of half of the population, but conveniently not the convocation of 14(13) who actually summoned him.
Hydaelyn was summoned by the self-sacrifice of those who summoned her. (hints that it could be 'the twelve')

Zodiark represents selfish self-preservation.
Hydaelyn represents selfless sacrifice for the benefit of others.

It wouldn't surprise me at all if that very distinction means everything towards the nature of the summoned primal. It is a Final Fantasy after all.
And what have the Scions done when invoking a summoning ritual so far? Louisoix? Papalymo?