STUFF THAT'S DONE:
A- Know the exact cause of death and the ailment
B- Have a way of telling if a cure worked

KNOWN STUFF:
A- This is more a disorder on the patient than something the planet is doing.
B- It's circumventable, as Walt and a few very select mages were immune to it
C- Eidolon stuff won't be sufficient or sustainable.
D- The devices used to create them was part of the issue (and more a reason why continued use of them should be discouraged)

UNKNOWNS:
A- How is this ailment still persistent given what it's origins were?  Why haven't previous ideas killed it off yet?
B- WTF is up with the air colors?
C- Why was Gina even needed by Ayane in the first place?
D- What the heck does that wisp have to do with any of this?

WHAT DO:
A- Need to find a sustainable resource of spirits - a very large quantity of them at that.
B- Need a way to affix them somehow.
C- Distribute this on a large scale

HOW?
Idea 1: Obviously, this is something Eden would probably be a natural answer to.  But that would require gathering her lost relics first.
Idea 2: Some sorta treatment chamber or something to correct the issue - but how the heck would one test this and what would be needed to make it?
Idea 3: Ayane had the right idea after all and this is all the crystal's fault. #yolo