Phantoms should be tameable (not rideable)

The Phantom would be a cool mob to make a pet, thanks to its interesting design and being a monster instead of an animal. Some people want to be able to ride phantoms, but I think it would work better as a hawk-type pet; the player could fire at a mob from any distance and the phantom could finish the job. It would also stay lower to the ground, adjusting its height based off its surroundings. By right-clicking it, it could perch on the player's head. It still doesn't like cats, though.

The player would tame a phantom by giving it a lead/leash and attaching it to a fence post. Then, the player would have to find a way to stop it from burning at daylight, whether that be with a roof or fire resistance potion. Once the sun fully rises, the Phantom would become "Pure" and change its appearance. Its owner will be whoever gave it the lead. It then acts as described above.

However, if it's exposed to moonlight without cover, it will become "Rogue", causing it to act like a regular phantom, but targeting all mobs that aren't its owner, even the owner's other pets. If the player doesn't have it in sight by daylight, it will disappear forever. If the player manages to keep up with the phantom, i.e. by using a lead, it will turn Pure at daybreak. A permanent solution is to craft a phantom nest, where upon spotting one the phantom will land on it and mark it for itself. Now, whenever it disappears, it will be found sleeping in its nest, with whatever loot it found in the wilderness.