One thing that I'm curious about, is whether Aether drained by Primals regenerates over time, or if it's gone forever. Aether seems to be tied to Hyaedalyn in an intimate way; she is weakened when Aether is abused, which is very likely why Ascians are so gung-ho on Primal summoning. Presuming that the summonings were to stop, though, would Hyaedalyn eventually recover, and return Aether to the world (including Aether-drained areas like the Burn), or is her current diminished state a permanent thing?

If Aether can be restored over time, perhaps the existence of a single Primal would not be that big a deal. That could be the rationale behind Ifrit's and Garuda's insistence on other summons being heretical - as long as they're the only one on the block, Hydaelyn can handle the strain, and they get to promote their agenda without worry of long-term harm coming to the planet via Aether drain.

The existence of the Burn might imply that lost Aether is a permanent change - but, on the other hand, the Burn was a pretty extreme case, and may simply take a long time to heal - time the Ascians are not allowing her, with their continued harassment.