(DISCLAIMER: I have touched nothing concerning Thornmarch or Coil, so I know of nothing concerning the lore there AND have yet to complete the MS Epilogue, which I intend to do today.)

I'm just completely spitballing an idea here but, would it be absurd to suggest that perhaps the Echo is a power much like what the Ascians have and their connection to that 'parallel' Hydaelyn? I know that Hydaelyn appears to choose those blessed with the Echo (I guess?) but would it be absurd if the Echo exists in a bloodline somehow?

So if we go off that, would it then also be possible that adventurers could participate, in the future, rituals to summons aetherically pacified Primals? Would allow for an excuse to summon more complex forms of primals at least, such as a smaller but more accurate garuda and Titan (Perhaps not ifrit) and would allow those beings to perhaps work together and whatnot.

If we assume that the parallel Hydaelyn and its worshippers, the Ascians, are beings of chaos and destruction, then from a logical standpoint those blessed with the Echo should represent Order and Life. So presumably, maybe we can find a way to summon primals and elders in a stable and permanently physical state.