I'd like to request a feature that removes the ability for the wither to attack other entities, so it should only attack the player.

A more complicated but robust version of this feature would be a fully customizable targeting feature. You could define which mobs any entity is allowed to attack or not, including the player. So you could say all sheep will attack players as well as zombies, for example, or say the Wither is only allowed to attack the player.

Honestly though, I just need the wither feature so that targeting feature isn't really needed but up to you!