Enderman and Player alliances/FRIENDerman NOT PETS (check detail for info)

Endermen are one of the more intelligent mobs, so I think they should be able to reason with the player and form bonds (NOT AS PETS, friends more so).

Say you hand an Enderman a helmet and chestplate while it's raining (so it'll protect them), they'll remember that moment as they go through their life, forming a friendship

When an Enderman is your friend they WON'T teleport to you like pets do, they just do their thing and may sometimes help you if you need it.

Benifets: If the Frienderman is nearby while your getting hurt they'll help you. If you look in their eyes they won't hurt you (but they will get annoyed). When you hand a Frienderman a chorus flower they'll be very happy and pick you up and will quickly teleport 4-5 times while having heart particles appear (along with a new happy Enderman sound) and after will give you a gift in return. If you hand a Frienderman certain blocks they'll build structures that you would normally see in the world (examples of this being village houses, temples, endertemples, ect) If they don't have enough blocks to finish they'll stop the progress until you hand them more of the according blocks.

Down falls: If you kill other Endermen while your Frienderman is nearby it'll attack you and no longer be your friend. The more times you look at the Frienderman's eyes the more annoyed he'll be, therefore starting to do mischievous things such as teleporting you far away from where you were at (you can give him a chorus flower to apologize)