My vision is that wizards should be scholarly people who are seldom seen as daring adventurers. The kind of arcane caster that lives alone in a remote tower and studies a lot. Sorcerers, on the other hand, are the more wild and free type. They love adventure more than a sedentary life, and they're a bit more dangerous in a bar fight than a wizard would be.
It seemed to me like the only option to differentiate the classes was to split the spells up. A new possible list looks something like this:
Sor/Wiz: Conjuration, Divination, Universal
Sor: Evocation, Illusion, Necromancy
Wiz: Abjuration, Enchantment, Transmutation
This is a bit more extreme than I proposed before, but I have something new to add to it later. This fits well into what I'm hoping for in several cases, but it leaves a lot of empty spaces because there are a lot of spells that I think should be available to both classes. I had originally tried dividing up the entire spell list by individual spell, but that was just a nightmare. This new list puts the bulk of the spells where I think they should go, but isn't really viable because there are enough important spells that are locked out for one class or another.
My solution is spell level adjustment! Sorcerers are good at the spells on the sorcerer list; better than wizards, so a sorcerer can cast that spell as if it were one spell level lower than the book. That makes magic missile a 0 level spell for a sorcerer, and I do believe I like that. Wizards don't get magic missile until 2nd level, but they get it. Wizards don't get 9th level evocations spells until they can cast 10th level spells, and that seems fine to me as well. If you need a meteor swarm, find a sorcerer! Spells that are on the sorcerer/wizard list retain their normal spell level.
There is still plenty of reasons to take a wizard adventuring, so they don't have to worry about vanishing from the players table. The sorcerers might be able to rattle off damage like a machine gun, but they will be quite a bit more limited when it comes to non-combat utility spells. As a side note, one thing I am heavily considering is adding in a rule that says sorcerers can not write or cast from scrolls. That fits into my notion of how the classes are different, and helps to buff the wizard back up in power.
Play testing this is a long way off. Warren has to finish his campaign, which he said would last 3.5 years (I don't expect it will last near that long) then I'm committed to running a published module series which I'll use stock rules for.
But in the mean time, I subject myself to your comments again, to see what you think about this.