Hawk Diesel
Adventurer
In most of my games, "slots" and "spell levels" are not in-game concepts, so there'd be no way to wish for one.
I disagree. Even if the concepts of spell slots or levels are not explicitly "in-game" concepts, I would argue that spellcasters are aware of the differences between kinds of spells and their relative power level. In character a spellcaster might not wish for an extra 9th level spell slot, but they could wish for an extra reserve or well of power to call upon their most powerful spells at will. Or something to that degree.
EDIT: Sorry, didn't mean to say I disagree with how your table handles things. But just to say that the OP's wish could potentially be made even without concepts like concrete spell slots or spell levels.