Strictly speaking Shaman can dump charisma negative and still poach a single Wizard spell per day, as long as he has positive int. It's just more rewarding to have positive cha since you can get more than one spell per day this way. Another way to gain access to all Wizard spells as Divine spells is a Shaman, Cleric, or Druid with the
Dreamed Secrets feat. Oracles have everything from Dreamed Secrets to
Ancient Lorekeeper archetype to Arcane Archivist revelation from the
Lore mystery to the
Spirit Guide archetype using Arcane Enlightenment as Shamans do (to get around the FAQ saying "Oracles have no ability to prepare spells" just get the
Versatile Spontaneity feat and
Magical Epiphany feats) and probably some other stuff I missed, including ordinary mystery spells.
By the way, with the
Quick Preparation feat, it should be possible to use
Balanced Scale of Abadar to give yourself prayerbooks once per week and quickly prepare the spells on them if you're doing partial spell preparation, but you'll need to advance Balanced Scale beyond max level with the
Evangelist prestige class.
Abadar's Evangelist boons aren't very impressive though (aside from the
Glibness SLA, that is), and this trick only comes live at level 13 (plus you get a dead level from Evangelist).
An easier trick would probably be to just prestige into
Daivrat and use
Prestigious Spellcaster to fix the level penalty while either scribing your own scrolls of anything you want to keep or transcribing those spells into your prayer book, if possible. Loremaster is still the best way to go on the PrC front, however.