(1) I suspect that UK ends up buying some VSTOL F-35's for Queen E.
(2) Installing catapults in the second aircraft carrier -- they probably didn't leave enough volume and mass margin in the current design to do that, even if it's only two catapults instead of four.
It's much bigger than some sort of auxiliary power unit that might be bolted into a spare storage locker ... much more money and re-design work needed.