It would be nice if you would morph into a certain mob that you would really be that mob.
For example, if you're a wither and low on health you will deflect projectiles like arrows. If you're a zombie pigman or wolf and you're getting hit by another mob or player, they will attack them.

This small but interesting details would make morphing fun IMO.

@Quizer9O8 yeah, that sounds cool, but, you know, I can do that only for vanilla mobs, and every feature like this might take some time. However, yeah, I'll try to implement it if it's possible or so.