Making nautilus more usable (2 block high mount)

My first idea getting a underwater mount that gives infinite waterbreathing was to use it against the only underwater thing to do, the ocean monument. However after forcing my way through i suffocated in every doorway and even the top boss room had barely any space to see. I urge the developers to try this out and see how painful it is. A VERY easy change to this is to make the mount and player be 2 blocks high. This would give the nautilus a use in the game and a viable way to take down the monument. Why have armour if the only thing to fight is drowned