I exhausted all dialogue options before killing him.

What I meant by that was the Greybeards don't posess the gift of foresight, Ulfric may not have intentionally tricked them, but he went onto use the Thu'um in battle. Despite this they still taught him before then. If that's the case a Nord could be sent to learn shouts without them knowing his true purpose.

This thread is kind of going in circles now anyway, it's pretty much accepted it isn't going to happen, it is theoretically possible, but very dangerous and very unlikely to happen.