I came up with a spell system variant that's remarkably close to Rasyr's (at first glance).
Simply put, you prepare whatever spells you like, as per PH rules. You cast exactly the same number of spells per day as before, but they don't disappear from memory when cast (instead you just subtract from your available spells). To compensate sorcerers and bards for the relative loss in flexibility, I've given them a bonus feat (eschew components, 1st for sorcerer and 5th for bard), and also added their "bonus spells" to their number of known spells.
We've been using this system for a year successfully. It makes all spellcasters more flexible, but - as a DM - I haven't found it overpowering.
-shaele
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Spellcasting
The spellcasting rules have been changed to a “template” system, which provides a little more variety in spellcasting.
Preparing Spells
All spellcasters except bards and sorcerers needs to prepare spells ahead of time. This involves prayer and meditation for a druid or cleric, or sitting and reading spellbooks for a wizard. It takes approximately 15 minutes per spell level to prepare a spell (cantrips count as first level spells for this purpose).
The number of spells that can be prepared is listed in the Player’s Handbook. For all casters, the number of spells they can prepare equals their base spells plus bonuses for high attribute scores (if the caster is a cleric, also add their extra domain spell to this total). Clerics can freely prepare standard spells or domain spells in any of these slots.
A spellcaster can replace a prepared spell with a new one, by mentally releasing the old spell and preparing the new one in its place (this requires 15 minutes per spell level, as described above). If he is interrupted during this process, he has lost the old spell, but not yet gained the new one.
e.g.
Rahl is a first level wizard, who can prepare 4 cantrips and 2 first level spells. He sits down and prepares (0-level) detect magic, light, mage hand, ray of frost, (1-level) magic missile and spider climb. This takes him approximately 90 minutes. These spells will remain in his mind until he chooses to replace them with other spells.
Casting Spells
A prepared spell is like a template, through which a caster can channel spell energy. The number of spells that can be cast in a day is listed in the Player’s Handbook. Clerics add their normal and domain spells together to determine the number of spells that they can cast.
Casting a spell does not erase it from memory, but counts against the number of spells that can be cast in a day. If a spellcaster runs out of spell slots, he can choose to “give up” a higher-level slot to cast a lower-level spell.
e.g.
Rahl can cast 4 cantrips and 2 first level spells in a day. In a battle with a goblin, he casts Magic missile, reducing his count to 4/1. He loots a nearby chest and casts Detect magic, reducing his spells to 3/1. Since casting a spell doesn’t erase it from memory, he could cast Detect magic up to 3 more times, or cast any other combination of spells that he has prepared, as long as he doesn’t exceed his maximum for the day.
Multiclassed Spellcasters
It is possible for a spellcaster to have levels in more than a single spellcasting class. In this case, the number of spells that he can cast in a day are combined into a single number of spells per day. When casting any of his spells, he subtracts from this common pool.
Spell lists should still be kept distinct, and spells for each class must be prepared separately. Also, spells are cast at the level of the appropriate class (not the higher of the levels, even if they are from the same spell list).
e.g.
Rahl is 5th level wizard, and decides to multiclass as a cleric of Mystra. He is now a wizard 5 / cleric 1, and prepares his spells for each class separately. When casting spells, he can freely cast from either list, but his spells take effect at the level of the appropriate class. For example, he could cast a huge number of Bless spells (using up all of his wizard and clerical spells), but each spell would be cast as a 1st level cleric.
