I really like the Readied spells mechanism from AU/AE, so I'm more inclined to like Wulf's proposal.
However, while I'll refrain myself from screaming "Broken !", I would probably add one of the following limitations
- a cap on the highest level of spell known, something like class level x2.
- Every full spellcasting class after the first gives a -1 to BMB
A side effect to the Readied spell mechanisms is that it blurs the differences between sorcerers and wizards casting styles (and replaces them advantageously).
Looking at their progression tables, I wondered if one class wouldn't be enough to represent both archetypes. Let's call him the Magic User
The Magic User chooses between two mutually exclusive (or not ?) feats:
The first one allows the Magic user to convert up to one spell slot of every level into two readied spells of the same level.
The second one allows the Magic User to convert up to one readied spell of every level into two spell slots of the same level.
Both feats can only be used upon readying spells.
Additionally, I would give a feat every 5 levels. I would add several feat chains or feat trees for representing school specializations or sorcerous bloodlines.
Chacal