I have a drawing for just that. Contacted my primary at the FAA, would have to make it a completely different part number and not a minor change to the regular bowl part number. Therefore every assembly with that bowl would also have a different assembly number, and all of those would have to be certified again for each individual model aircraft it could be used on.
And on, and on, and on, and well, I'm sure you get the picture. They do not make it easy, and the cost to just add a simple hex makes it not worthwhile since the current design still works well.
--Brian