Untested Thought: 3e Wizards...

This is the core of the spellcasting rule I've been toying with for "Nutshell Fantasy", re-written for 3e. It assumes that the Wizard is the default caster...

At the start of the day, the Wizard chooses any 6 different spells to prepare. These can be of any level up to the maximum that the character can cast normally. (So, a 9th level Wizard could, if he wished, prepare 6 different 5th level spells if he wanted. Bear with me.)

A spell can be prepared for at-will, per-encounter, or daily use. The Wizard can prepare any spell for daily use, a spell of up to two less than his maximum for per-encounter use, and a spell of up to four less than his maximum for at-will use.

(So, our 9th level Wizard could prepare a 5th level spell for daily use, a 3rd level spell for per-encounter use, or a 1st level spell for at-will use.)

So far, so good. And as should be obvious, when the Wizard casts an at-will spell he of course retains the use of the spell. Indeed, he can cast it again next round (or even the same round) if he wants. When the Wizard casts a per-encounter or daily spell, it is expended for the time being.

When the Wizard takes a short rest, he regains the use of any expended per-encounter spells. At this point, he also has the option of switching out any of his prepared spells for any other spells of his choice, with two caveats:

1. Once a daily spell has been cast, it cannot be replaced until the next day. That slot remains expended.
2. Once a spell has been cast as a daily spell, it cannot be used again.

(What this means is that if our 9th level Wizard prepared teleport as one of his spells and then cast it, then when he took a short rest he can now only prepare 5 spells for the rest of the day... and teleport cannot be one of them.)

The effects of metamagic would apply normally. Note that a "metamagic version" of a spell is considered to be the same spell for the purposes of the "six different spells" clause. That is, a caster could not prepare both a maximised magic missile and also a normal magic missile.

Note that under this model the Wizard's Intelligence does not grant him additional spells per day. This is intentional - in 3e as it stands, that stat at once grants extra spells per day and increases the saving throw DC for most spells and controls the highest level of spell that the character can cast at all. This is really too much overloading, and makes that stat of overwhelming and unreasonable importance to the Wizard.

It's also worth noting that this approach at once makes low-level Wizards more powerful and makes high-level Wizards less powerful. Given the relative balance of the classes, this is actually a good thing.

So, any thoughts?