What I originally proposed, based on the 3.5 spellbooks of these classes:
Looking at it now, I'd say the Blackguard spellbook I made is a bit underwhelming (though Divine Favor is a pretty powerful spell), more could definitely be done there. Then again, it's mostly faithful to the 3.5 version, that's not to say we shouldn't add more fun or interesting spells to the list, but that's for the devs to work out.Blackguard (Wis-Based).
1st level: Inflict Light Wounds, Cure Light Wounds, Scare, Doom, Magic Weapon, Summon Creature I. [Divine Favor, Protection from Alignment.]
2nd level: Inflict Moderate Wounds, Cure Moderate Wounds, Darkness, Eagle's Splendor, (Bull's Strength), Summon Creature II. [Resist Elements.]
3rd level: (Inflict Serious Wounds), Cure Serious Wounds, Protection from Elements, Summon Creature III, (Contagion). [Greater Magic Weapon.]
4th level. (Inflict Critical Wounds), Cure Critical Wounds, Freedom of Movement, Poison, Summon Creature IV. [Fear.]
Assassin (Int-Based).
1st level: Sleep, True Strike. [Camouflage.]
2nd level: Cat's Grace, (Darkness), Fox's Cunning, (Invisibility).
3rd level: Magic Circle Against Good. [Neutralize Poison.]
4th level: Clairaudience/clairvoyance, Freedom of Movement, Poison, (Improved Invisibility). [Polymorph Self.]
Those are the spells that are in NwN's script. The spells in parentheses are already integrated in some way in the game, as feats. Of course, this is just a template, the developers are free to put whichever spells they see fit.
Brackets are thematic spells that I thought of.