XP Phantom Mechanics

Phantoms should spawn for 1-3 nights in a row at every 15 to 20 XP increase. Since Phantoms would spawn less they should be more dangerous and spawn in larger groups. (I think all minecraft mobs should spawn less but have more danger to limit the end game nuisance feel from them). 

With phantoms being more dangerous, fireworks should cause extra damage to phantoms when shot out of a crossbow. Fireworks should have two large kill radiuses. The smaller center radius being a one shot kill to phantoms and the larger outer radius being a two shot kill. 

Witches should be able to spawn and ride phantoms occasionally. The higher your XP levels are should increase the chances of a witch spawning with a phantom. They will be able to throw their potions from the top and also descend upon the player from the phantom using slow falling. 

Finally, witches should ride phantoms during the later raid rounds. Phantoms wearing helmets could protect them from the sunlight during these raids and would honestly add a lot of fun the raid experience defending the land and air.