Sorry this is so late to the discussion but I've got a radically different idea that may work for your character background, feed well into archivist AND enhance the utility of that class immensely. But it will take getting your DM to buy off on a slight variation of a class first- although I think the variation works very well for the background you've got going. A
divine spellthief!
The only change to spellthief would be exchanging arcane spells for divine ones. This is hardly the cloistered cleric or other respectable job background you've discussed so far, but hear me out...
So, you came from a family of clerics and such. That explains your inclination to the divine. But for whatever reason- the gods themselves, or just the church lifestyle, didn't appeal to you. (which also fits with an archivist- casting divine spells w/out praying for them sort of flies in the face of accepted dogma) So your the black sheep of the family. Maybe you figured if you couldn't
tap into the divine the normal way you'd
break into it instead- hence spellthief. Then as a first level upstart, you stole a spell at exactly the wrong moment and got yourself in some heat way above your CR, and the MIBs show up with their offer. You chose the smart course and work for them, burying yourself in a librarian role hoping to disappear. Your research moves your spellthief background into archivist- and thus to the party. (Heck, you could even start of as an
arcane spellthief with your research allowing you to exchange
arcane for
divine, which leads straight to archivist. After all, archivists are effectively "stealing" their divine spells.)
If your DM will go for it (and hopefully it'll be an easy sell since it does make a lot of sense) your set. Now for the awesome part that enhances your utility as an archivist as far as you want to take it- take the "Master Spellthief" feat from Complete Scoundrel (but again- divine, not arcane) at 3rd level. This would let your spellthief and archivist levels stack for determining what level spells you could steal and for archivist caster level.
That feat is what makes this combo shine! Not to mention, well worth giving up those cloistered cleric domains. The main limitation of archivist is relying on the DM to provide you with prayers and scrolls to copy into your book. When was the last time you found a prayerbook as loot? Probably never. But, if you could
steal spells from your enemies... that's a different matter. Now, every divine caster you face is a potential font of knowledge for your prayerbook. And, when you have some downtime, you could lift spells from the cleric in your group- if he's willing.
See, I agree with Nifft- as a full caster your spells ARE your main class feature. Dark knowledge is an awesome ability- but it pales in comparison to the versatility of spells. Think of it this way, an archivist is essentially a cleric who exchanges spontaneous casting and turning for dark knowledge and a few other minor abilities. If those exchanges are equal then you have to consider this- would anyone consider turning and spontaneous casting the thing that makes clerics a good class? Doubtful. It's the spells. And since clerics effectively "know" every cleric spell ever, while archivists are limited to what's in their prayerbook (which, again, is limited to what the DM feeds you), then clerics still come out on top.
So even the playing field and steal the spells you want to copy into your book. Heck, your DM will probably thank you for it since he won't have to gen up prayerbooks and scrolls for you to find. Anyway, it's another option to think about- albeit a very effective one.
