Spells set as domain/school spell should only ignore one preparation, not all of them

This is not really a bug but more of an enhancement.

A spell marked as domain/school currently ignores all it's preparations, so a domain/school spell that is prepared three times is not consuming three spell slots.

However, wizards and clerics only get one domain/school slot. An evocation wizard who wants to prepare fireball three times, once in the school slot and twice normally, has to duplicate the spell and prepare both once and twice, respectively, with the once prepared spell set to domain/school.

It would be nice, if domain/school spells would only ignore one of the slots they are prepared in so that only one copy of the spell is needed.

However, my knowledge of classes is very limited (especially archetypes) so I don't know if wizards/clerics are the only classes getting domain/school slots and if it's always only one slot.