A25: Dragonwrought Kobold will get you there. Lore Drake + Greater Draconic Rite of Passage gives you three spellcasting levels ahead of normal, so a basic Sorcerer 6/Ur Priest 1/Mystic Theurge 9 (note: you'll need to PrC that Sorcerer level into something else to get the necessary Ur Priest saves, and you'll need a Sanctum Spell or Earth Spell trick to qualify for MT at UP 1) would give you 9th level Cleric spells at 15th level and 9th level Sorcerer spells at 16th.
An easy way to get your saves up as needed would be to use the Dragonblood prerequisite trick to take the Dragonborn Sorcerer 7 ACF at level 2, giving you a Fort Save of +2 at level 2 and a Will save of 5 at the same... in addition to a BAB of +3. From there any PrC that gives good Fort saves would finish the job (you probably also want more skill points). You did say dubious or not, after all.
JaronK