Add the ability to travel to the end, much like the nether, but here its a custom build, like a reverse spawn.
maybe you have to defeat something or pay a price to get in, but this area would sell new items, spawners, or maybe the custom books that are currently unobtainable?
this would be a really cool feature.
you could also give access to another warzone in the End that would have new enemies, loot, towers, and better crates than at the normal warzone.
now I know that would be a lot of building, maybe you could hold an event much like the dual arena event, for others to build you stuff to put there.