The Sky Shrine is a block that makes Elytra renewable but cost one to craft

In looking to de-monopolize flight on large servers, I took care not to make End Ships worthless. My solution is the Sky Shrine, a utility block that once built, crafts Elytra from 100% renewable inputs, forever and for all players. - How to obtain: Shrine Shards can be found only in chests of the Sky Fortress, a rare aerial structure. Crafting 8 Shrine Shards with an Elytra makes the complete Sky Shrine, meaning a player may have to explore multiple Fortresses to craft 1 Shrine. The Sky Fortress may occur high in the Overworld or End, or in a new Sky Dimension. Alternately, do away with the previous and instead make it Echo Shards so Ancient Cities retain value in Hardcore mode. - Protecting the value of End Ships once a Shrine is made: The product Elytra is a variant that cannot be used to craft further such Shrines but has say, bonus durability to sugarcoat this devious trick. There must be a reward for having multiple Shrines, at least for the kind of player who would seek to have multiple Elytras. - Input resources: All inputs must be renewable, but neither too easy nor too hard to obtain. End Crystals perhaps? The Shrine takes time to make 1 Elytra, similar to brewing or smelting, so there is reward to making multiple of them. - Who would want it? Most singleplayers would want only 1 Elytra with Mending/Unbreaking, so extra End Ships have already lost value to them. However, those who want multiple Elytra, possibly for friends, will get what they want.