Alexbrine

While this is listed as a Previously Considered Suggestion, I am not asking to add this directly to the game, just as a command and as a cheat feature that could be enabled/disabled.

/summon alexbrine

If the setting is enabled, it could rarely spawn in the world. Or, you could talk to it to summon it, or you could build one of those golden altars which would summon a lightning bolt and make Alexbrine appear.

Behaviors:

• She typically attacks by punching the player with her fists, which won't do much damage.
• If you battle her, she will eventually get bored and leave you alone.
• When two players are in a world, she would attack one of the players with her fist while disguising as their friend by mimicking their skin (even mimicking their name too).
• She can teleport like an enderman but lacks particles.
• She does take damage like a normal player, but their health regenerates so quickly that they are essentially immortal.
• Nearby mobs and animals will be hypnotized to attack the player, and they will have white eyes.
• It could make leaves vanish from trees.
• She will rarely spawn with a diamond sword.
• She will also be connected to a chatbot, and communicating with it would change its behavior.
• You could also befriend Alexbrine or work for them, and get them to do things for you like give you diamonds, fight a player for you, or give you their powers.

They would also have a floating castle in the sky which you could find good loot at.