cultural differences aside...
I've never been thrilled with the notion that the charisma score should be lumped together with good looks. Anyone here ever meet an absolute babe that was a jerk? Of course you have. How about an average person that has "animal magnetism"?
I've got friends that women rate as "nothing special" to average looks, but somehow are totally attracted to them solely because of their personality. Most of the great leaders of the world are not physically attractive, in fact they're just the opposite most of the time, but they have powerful personalities and what I would attribute to be an exceptional charisma score in game terms.
Personally, I could go with divorcing the physical attractiveness from charisma entirely, and have the player make their character as attractive or disgusting as they wish. If they think by making their character drop-dead gorgeous is going to help them in some way they can think again... or they can have a comeliness stat like in the old unearthed arcana. I think that if good looks is somehow going to mechanically affect the game there needs to be a quantifyible measurement of it. If all players can accept it being a die roll, then fine, let them roll for it, and they can deal with it. A couple of us have had disputes on whether comeliness should be used, and we've pretty much dropped it from our game. In other games such as Shadowrun, we have a simple edge or flaw that can be purchased to utilize good looks, otherwise I just assume that everyone's characters have average looks.
I do like the idea of having a feat for good looks, but I think there's also the potential of abuse as the benefits could stack with other feats, giving a bard or a thief an ungodly diplomacy and bluff score.