Mob for distance attack

I was thinking, how about adding a mob that is the player's ally and attacks from a distance? I know we have the snow golem, but snowballs don't hurt, so it would be great to have a mob to help the player against hostile mobs. It could be a mob that has to be tamed or a golem. I have two attack options in mind,(let the community decide). Option 1: I could attack fast but would do little damage and would be at a medium distance. Option 2: it would do a lot of damage but would attack slow but would detect enemies at long distances. This mob would help the player against mobs that attack from a distance like skeletons, wither, blaze and maybe other players. P.S.: It could also attack in water, but it would be with some kind of nerf.