Allow Directly Setting Target
Summary
A command called 'target' or 'setTarget' sets the mob's target.
Usage
This could be useful for more complex boss fights and more interesting behavior within the targeting system. For example, let's say there is a boss that looks for the weakest person within a group of people. It then targets that person. Another example would be to attack the person who is healing other players.
Value
This could help create more dynamic behavior within boss fights.
Priority
On a scale of 1 to 5, I'd give it a 2-3. While this mechanic could be very useful to some, it isn't at the top priority.
Implementation
I'm unfamiliar with NMS functions, but in spigot there is a function called LivingEntity#setTarget, which sets the target of a mob.