Two fielding gloves/mitts at once.

As far as I know there's nothing in the rules that prohibit a fielder from wearing a glove/mitt on each hand.

There are obvious benefits, such as never having to backhand a ball.  Before you dismiss this with "how will the player" throw, calm down and think it through.  Baseball people are instinctively negative about any change, which is one reason baseball is stuck in the mud.

Watch how former MLB pitcher Jim Abbott, who had no right hand, switched the glove from his stump to his hand and off again to throw when he fielded a batted ball.  For two handed players it would be much easier.  Just drop the glove/mitt off your throwing hand when you know that you will need to.  Just drop it.  On the ground.  You can pick it up later.  Pretty simple, right?

So how come nobody thought of it before?