Improved NPC AI and more hostile and non - hostile mobs would be one of many things!
[b]Zombies[/b would break blocks if they had specific tools. For example if you had wooden walls and a zombie has an axe, he would slowly tear it down. They would attack in groups since they are the weakest type of mob. There need to be more diverse zombies like a Sprinter or a Bulky but really slow zombie.
[b]Skelletons[/b] would run backwards if you get too close to them and there need to be fast, since all they have is bones.
[b]Spiders[/b] need to shoot out cobwebs and a new " Spider Matriarch" would lay Nests that could swarm you if you do not deal with it quickly enough!
[b]Endermen[/b] Could have an abillity to teleport you with them!
[b]Pigmen[/b] could have a slam ability
I have many more Ideas but im kinda lazy to write em down
