I want to talk about tempering

[LineageRazor]

Note that both Nael and Lousoix had the grip of the primal relinquished off them, The canonicity of that might be questionable but I believe that the effect of tempering can be removed

I think that in Nael's case, at least, it was explicitly stated that Bahamut relinquished his hold on Nael because Nael had died and was no longer of use to him. The "untempered" Nael we witnessed was basically Nael's ghost, just prior to dispersing into the Lifestream. It is certainly possible that tempering ends with an individual's death, in all cases - though if they desire, a sufficiently powerful Primal can choose to hold onto the soul after death and construct a new body for it (again, as was the case with Nael). There's no point in holding onto a disembodied soul with no body, though, so Primals generally don't bother.

I think the primal has to be currently existent to maintain tempering after death, though.

It could be that aether once committed to a primal becomes incompatible with Hydaelyn. In such a case, the aether could very well disperse and exist but still deny Hydaelyn power. If the Ascian-derived summoning methods were part next-level plotting, it may also be the case that such dispersed aether remains compatible with Zodiark, should it (he?) ever need the aether.

I like this theory, and it makes a lot of sense. Primals act as a kind of "converter", changing Hydaelyn-aether into Zodiark-aether. The biggest flaw I see with it, though, is that Ascians seem just as gung-ho on defeating Primals as they are on summoning them. Wouldn't it make more sense for them to promote keeping the Primals around as long as possible to process as much aether as possible before they're destroyed? In ARR, the Ascians were clearly enthusiastic about the WoL defeating Primals, all part of their mysterious plan...

Maybe the act of summoning converts a lot more aether than is converted by the primal just passively existing? In that case, a cycle of repeatedly summoning and destroying a primal would make sense under this theory.