Rust and Ruin its scary how much sense this makes.
Now, realmatics-wise, if Ishar can find a way or can successfully recreate what was done with Siah Aimians, according to this theory, it opens the door to all kinds of physical manifestations of spren (Cryptics were tried, clearly).
But why stop at spren? If this is something that could be done feasibly end-of-cosmere, we might end up with a whole host of new sorta-human races! Would seons work?
And would Cognitive Shadows? Assuming this theory is correct and such a thing has been done before, I don't see it too far-fetched to then assume that Cognitive Shadows (which can even enter Nahel bonds with humans, funnily enough) could re-enter the Physical Realm.
And, SH/BoM: