Something I have considered and am now reconsidering is treating sorcerer spells like psionic powers. Those unfamiliar with psionics...well, instead of spell slots and spells per day, the psionicist gets points which they spend to evoke powers, and they can spend more points to augment those powers as they see fit (increasing damage, extending duration, adding secondary effects, etc.)
In my experience, psionics come with their own set of pains, but (like many non-standard ideas) they work if used responsibly.
A spell point system truly opens up the caster to (near) complete freedom. He could throw everything he has into his fireball, augmenting it to max damage, but leaving himself spell-less until the next day.
Here is a good basic spell point concept. What it lacks is the complete freedom of augmentation (this one only allows for increasing of damage dice from the minimum).
Here's an example of a psionic power and the augmentation possibility: The first-level power force screen (the psionic equivalent to shield) allows this: "For every 4 additional power points you spend, the shield bonus to Armor Class improves by 1."
And another: This is found in the power energy bolt, a third-level Wilder power: "For every additional power point you spend, this power’s damage increases by one die (d6). For each extra two dice of damage, this power’s save DC increases by 1."
In summary, I'm considering changing sorcerer spell slots to spell points, using an amalgam of the variant spell point rules and psionic power augmentation. If I do that, I'll remove the bonus feats from the sorcerer.