Well it depends on how you define spell list. I can't find a RAW definition of it anywhere, but I'm under the impression that it means something along the lines of "list of spells a class may learn." Which would make this work perfectly fine.
Thanks for bringing that up Plz it was helpful and I think I'm almost done with a pretty great spellcasting build that has access to every spell in print on a whim.
As for the Archivist/Chameleon idea, you can get every spell ever, but you have to go find and learn them which can be expensive and inconvenient.
I think you are going to be fighting an uphill battle. With the expection of the archivist and chameleon, classes specifically draw spells from their spell list which is listed under class's "Spells" class ability. While there is not an entry called "Spell list" in the SRD that gives a description of what that means specifically, there is a tab for "Spell Lists & Domains" which goes through what spells are on who's list. Furthermore if you take the stand that there is no explanation in the book for what a spell list is, you are not in the position to freely declare and define this ability as per the RAW. The omission of the words "spell list" under the archivist's spell casting entry and the use of the words "spell list" under the Eldrich Master's Spell Dilettante ability will be hard to circumvent.
An archivist casts divine spells, drawn primarily from the cleric spell list although he can eventually uncover, learn, and prepare noncleric divine spells."
The Archivist/Chameleon trick works much better with scribe scroll feat and the extra spell known feat. 2 levels of chameleon grants the free floating feat each day, take extra spell known and scribe a scroll of the spell you want. Change to another spell the next day and repeat. Costs money, but not all that much.
Option 2 for is for a good archivist. Take ancestral relic from the Book of exalted deeds. Ancestral relic lets you effectly sac gold to craft without any pre-req's, but only increasing the value of the specific relic with a gp limit based on level. Take a book relic, sac gold to the ancestral relic, and the added gp value you are adding is spells or scrolls. If you can do spells directly it is easy to get any spell since no-prereq's are required. If you are only allowed scrolls, copy scroll into you spell book and then read the scroll dropping the relic's cost allowing for the next scroll to added.
Both of these abilities are based on alternative sourced spell feat making all spells both divine and arcane.
My personal favorite build for the Eldrich Master is:
Bard 2/Cleric 1/Bard 2/Eldrich Master 4/Dweomer Keeper 1/ Sublime Chord 1/ Dweomer Keeper 9
Selecting Cleric as your added list, you can pick Bard, Cleric, and Sorcerer spells with the sublime chord. The level 3 arcane spell requirement is met with the Elrdrich Master's Spell boost ability granting a spell slot one level higher than you can cast. Bard get level 2 spells at 4th, so level 3 with Eldrich Master.
Feats: Extend, Persistent, Divine Metamagic Persistent, Alternative Sourced Spell, Spell Focus Transmutation, Ability Enhancer, Spell Preparation
Ability enhancer increases all ability score bonuses by +2 with Transmutation spells. Alterantive Sourced spell makes all your arcane spells divine for divine metamagic. Spell Preparation might be needed for that because alternative sourced spell specifics you can prepare spells as the other time, not just cast them spontaneously. Grab every spell that increases Cha, there are alot. Add in Fell Energy spell and Kiss of the Vampire to increase the effectiveness of all your buff spells by an additional +2. You can easily hit a Cha of 70. Oh, and some of your best spells are supernatural with Dweomerkeeper so they cannot be dispel or disjoined.
