Just make the staff using the rod rules, like the rod of the python, setting the "X times per day" for each spell effect.
To enable staves to recharge, I am thinking one could add a dedicated pearl of power to the staff. As long as the pearl was at least as high level as the highest level the spell could cast, the staff would recharge one spell per day. Because the pearl is dedicated to the staff, it would cost half the list price of a standard pearl.
Multiple pearls could be added to a staff if one wanted it to recharge faster.
Sound reasonable?
Thank you for reinventing the augment stone of recharging. Limit one augment item per magic item. Hopefully augment items will be in the new edition of Pathfinder.