An extension of the idea:
D) Extra components; I was thinking along the lines of some higher level spells requiring certain environments (You found a copy of Ardent Darts of Flame (Scorching Ray), but it only functions within a volcano), lifestyles (Fortitude of the Corpse (False Life) requires that you wear nothing but funeral garb while you have it prepared, with failure meaning you lose it entirely), or dead languages (Open The Stubborn Gate (Knock) requires that you can read (and speak!) a long-dead form of Dwarven.)
The main idea is that you can use spell research to make them more usable. You found Ardent Darts of Flame - research and experimentation shows that it is the humming crackle of the volcano that is required for the spell, and further experiments show that a "good enough" approximation of the sound is enough to make it work. So you can use a Verbal component instead of the Environmental component.
E) Societies of Arcane (or Divine) Fellows. Basically, instead of getting the full list of 1st level spells to pick from, you get a list of teachers to pick from, each possessing a smaller list of spells that they, personally, know.
I would go with maybe 10 or 11 spells each - drawn primarily from the PHB and the SpC. Maybe have some sort of ability to trade off spells on the list for "advanced" spells - think 1st level spells with a specific +1 Metamagic applied to it permanently, or a Cantrip with a permanent +2 Metamagic. Advanced spells would receive the benefits of Spell Thematics with regards to the guy who taught them to you - they are a masterpiece of arcane artistry.
In other words, if you study under the Collejum Arcanit, they have a wide choice of spells - you'll find most of the 1st level staples there. On the other hand, studying under the Archlich Uturius the Mad† gives you a much smaller selection, but you do get access to his signature spells, the dreaded Soul-Breaking Whisper (Sonic Snap with Fell Drain permanently applied to it) and the much-sought-after Black Sun Aegis (Mage Armor with Fell Energy Spell permanently applied to it).
Raiding a different group to get access to some of their spells is not only expected, but encouraged.
† OK, so he's just a Necropolitan Wizard, but he says he's an Archlich, and that's what really counts.