I don’t feel the ability to obtain a chance at a Purge Thrall that can repair a Legendary item takes away from its exclusiveness. I think being able to repair something that would otherwise be considered thrash is reasonable, maybe if it’s been repaired it has less durability. If you continue to be careless and break the item receptively eventually it will be zero durability (unrepairable).
I definitely think this mechanism is already in the game, just not through the use of a “Blessing” the new oils do exactly what you suggest, although not permanently.
I don’t feel that the Unnamed City is quite end game as you can complete it’s rotation well before 60. However I do love the Unnamed City, I farm it a lot myself. I would love to see it get a bit of an upgrade in terms of adding drops to the Green Dragon. Adding a few new bosses. Adding new Legendaries, Short Swords and Great Axes, some new armors perhaps. I digress.
Also I think that this post has a great idea for end game players: