I came up with a workable Bonus Feats for high Charisma rule on the WotC boards. In a nutshell, this is what it looks like:
Sorcerers and Bards get their powers through Charisma because of "inborn talent and ability". High Charisma characters are described as "confident" (PHB p10), the MM says Charisma represents "sense of self" (MM p298) and the flavor text for the "Force of Personality" Feat (CV p109) says "You have cultivated an unshakable belief in your self-worth. Your sense of self and purpose are so strong that they bolster your willpower". The "unshakable belief" and "bolster your willpower" parts are what the Feat is about, but "self-worth" and "sense of self and purpose" are Charisma-related.
A higher Charisma character can push themselves harder to achieve, and draw upon more innate talent, than a character with a lower Charisma. Abilities that are inborn or evoked rather than learned are often represented through Feats.
A character gets one bonus Feat for each +1 bonus they have for a high Charisma score. For example, a character with a Charisma of 14 gains a bonus Feat at 1st and 4th levels. Any Feat that represents an ability that is inborn or evoked can be chosen as a bonus Feat (i.e. Alertness, Draconic Heritage and Extra Rage are OK, Exotic Weapon Proficiency, Cleave and Arterial Strike are not).
Cha Bonus Feat at
12-13 Lvl 1
14-15 Lvl 1 and 4
16-17 Lvl 1, 4 and 8
18-19 Lvl 1, 4, 8 and 12
etc.
Like Intelligence vis a vis skill points, a Charisma score raised temporarily through spells or magic items wouldn't grant bonus Feats (but a Charisma score raised permanently through a Wish or levelling up would).
A character receives one Flaw at 1st level for each –1 penalty they have for a low Charisma score and can buy off the Flaw by improving their Charisma score.
I also came up with a variant Action Point-like system, based on Charisma (not to be used with the bonus Feats option - I just like to brainstorm ideas). The flavor text is similar to the text used above (AP usage always struck me as "pushing oneself harder to achieve" than "calling upon luck"), but the effects are different:
A beginning (1st level) character starts the game with 1 Action Point. AP can be used once per day.
You can spend 1 AP to improve the results of an attack roll, a skill check, an ability check, a level check or a saving throw. When you spend an AP, you add the result of a roll of 1d6 +/- your Charisma modifier to your d20 roll to help you meet or exceed the target number for the roll. It's possible to get a negative number when spending an AP. You can also spend 1 AP to stabilize (if using a house rule where characters roll a Fort save or Con check to stabilize, AP use is covered as above).
If your character is 8th level or higher, you can roll more than one d6 when you spend an AP (and use the highest of the die rolls):
Lvl AP Dice Rolled
1-7 1d6
8-14 2d6
15-20 3d6
NPCs have AP as well. It's up to the DM to determine whether or not an NPC has spent their AP at the time of the encounter (in the same way the DM determines whether or not the NPC has used spells or x/day class abilities).
Permutations:
* Characters have 2 AP/day at levels 8-14 and 3 AP/day at levels 15-20.
* A character may spend 2 AP to get one more daily use of an x/day class ability.
Anyway, just some ideas I've been working with. I'm not exactly sure what I'm going to do when I start my next game, though.
MadBlue