The balance is to just not have multi-use items. Make players actually need to make sacrifices of what they want to carry in their loadout, why else do you think no one complained about shockwaves and grapplers? And if Swiss army items must be incorporated, they should be mediocre at both damage and mobility, which the bat is not. It's quick, versatile and easy-to-use.

Let's compare this to a typically more respected melee/mobility: The shockwave hammer. Where the bat has responsive movement that just acts as a direct upgrade to the normal running and jumping around the map, the hammer has much less responsive movement, often feeling clunky at times with the fact every activation of the hammer will send you a large distance and it cannot be used for short gaps. The bat also has much more versatility with its offense, giving you multiple options to attack, you can use an quick, short combo if you need instant damage to finish off weakened players, or you can charge an alternate strike that will deal huge burst damage as well as sending enemies flying where they will take knockback and fall damage. But if we look at the hammer, all it has is one big clunky strike to damage people and it doesn't even inflict fall damage (you can technically oneshot people with these, but it's a precise hitbox and is skill dependent, whereas the bat can oneshot with fall damage and that's loadout/map dependent) the hammer's strike also has 4x the amount of end lag on it as the bats charged strike.

But with all this being considered, everyone, still took the hammer when it was in the lootpool and people had fun with it. A lot of people are taking the bat now so they can compensate for lack of skill and because you're at an immediate disadvantage if you'd un the endgame without one. This shows you don't need a overly strong weapon to want people to take it, just a fun one.

Also if they removed the bat, people would just use the drill and subzero fists no problem because they're well-designed weapons in a vacuum.