A Mob that can fight for the player and use weapons

Dear Minecraft Team!

I would love to have a Mob in the game (soldier like), that can fight for the player (choose witch mobs) and uses the weapons the player give to it (with right-click). This Means, it can use: Swords, Axes, Shields, Spears, Bows, Crossbows, tridents, ... . The player should be able to decide (in some sort of setting) which mobs and players it should attack. There, the player can also determine how it should fight: Walking Backwards, standing still, walking frontwards if the enemy is near (and if it should return to his position after killing the enemy), or hunting the enemy(s) down all across the world! 
This would be such a cool and useful feature, that would make the game so much better!

If you think, this wouldn't fit in the game, just make, that it needs to be summoned with commands.

-Marc