I'm looking for spontaneous casting classes with a spell progression comparable to wizards or clerics, meaning they gain access to a new spell level at every odd caster level (1st at L1, 2nd at L3, 3rd at L5, etc., to 9th at L17).
Have any spontaneous casting classes with this progression been published for Pathfinder? Do any of the archetypes or published variants/options allow this progression for existing classes with spontaneous casting, or grant spontaneous casting to classes that have this progression?
I'm pretty sure that the slower progression is simply a product of being a spontaneous caster, to my knowledge there is no spontaneous caster with fast spell progression
I'm not aware of any. Even the Ley Line Witch archetype, which is a spontaneous caster, trades out her normal spells per day for the Sorcerer's progression. It's just one of those legacy things from 3.5 that has become an ingrained convention, and I don't think it's likely to change.