ok so i thought of the ender dragon that shoots fire balls and all of that. BUT it doesnt perch, adding some difficulty to the fight. then use some simiar mechanics like the flowers in the bee fight but its a different item for the crystalls. finally, add rare items insted of xp when the dragon dies (prismarine, farm land, maxed items, stuff like that). finally, skip the end citys and just add a portal like the portals at spawn. you can add custom realms and stuff to discover in a 10,000:10000 to a -10,000:-10,000 range. i hope you enjoy my suggestion for the end fight.
Nah I think that the end cities are essential and they should add them.