Oh, man, something crazy just occurred to me.
First off, what if the real reason the Ellimist wanted to save the Iskoort in #26, had nothing at all to do with showing the Yeerks a way around parasitism? That explanation never really made much sense to me in the first place, given how far away the Iskoort homeworld was from earth; the Ellimist must have known that the war would be long-over before the Yeerks and Iskoort ever made contact.
Instead, ponder on this. The Ellimist's original homeworld, Ket, was covered in uninhabitable sulfuric swamps, which was what forced the Ketrans to live on the crystals in the atmosphere instead. The Capasins destroyed the crystals, but we have no reason to assume that they wouldn't have left the planet itself otherwise intact.
The Iskoort homeworld (perhaps not coincidentally) has a surface covered by very similar sulfuric swamps. Much like the Ketrans, the Iskoort were thereby forced to live far above the planet's actual surface.
So, here's the revelation that blew my mind: what if the Iskoort homeworld actually WAS Ket?! What if, what the Ellimist wanted to save from Crayak's corrupting influence, was not the species, but the planet itself?