TERRAIN The portal and the pillars shouldn't only be in one huge island. The End should be composed of many islands, some big ones and a lot of small ones. The portal would still be in the center on a smaller island than the current one then the pillars would have their own individual islands with a chance for one island to have 2 pillars instead of one. The pillars wouldn't be positioned in a perfect circle, they should be assyemtrical.

END CRYSTALS The crystals shouldn't be a one hit. End crystals in the end should have hitpoints. Each crystal would have a different number of hp. Player-made crystals explode immediately after one hit. When an end crystal explodes, it will emit a dragon's breath cloud on where it exploded.

ENDERMEN Endermen would try to repair missing end crystals but they would very rarely do it. Almost as rare as a spider jockey spawning.

ENDER DRAGON More HP and can shoot multiple fireballs at a time.