Tailed beast: This is the last thing I think should implemented as it would require a lot of work, but in short this adds giant boss fights to the game that spawn randomly and when it spawns you can try to fight it along with other people and when you kill it you can attempt to seal it in order to gain a tailed beast which would give you minor buffs to your character. While you are a jinchuriki you can not go in buildings because it would be unfair to hoard tailed beast. The chances of sealing one is extremely low and they are extremely difficult to kill so it requires a lot of teamwork and coordination to kill and seal one. Some buffs could include a buff to fire damage, wind damage, a buff to taijutsu, a buff to speed, buff to regen, passive wound healing, etc etc. Nothing to overpowered but something to give you an edge over non jinchuriki and to make up for the new lack of being able to go into hospital or hide in shops.