I really like this theory! I definitely feel like Radz-at-Han comes before Sharlayan in terms of locations we can visit. I'm feeling Radz-at-Han being the Crystarium of Endwalker whilst Sharlayan will be the more endgame Eulmore zone.

I also have a theory that the reason we get pushed away from Sharlayan is tightly linked into this "Coming Disaster" that we keep hearing about. I think Sharlayan have also looked into this, predicted the outcome and have discovered how to avert it. Them intervening at this current stage actually causes the disaster or causes it to be much worse and so they have to push us away for the time being. This is why Fourchenault took such strong actions towards the twins in the most recent MSQ to attempt to push them off the current path they are walking.