If you want beauty to be a part of CHA at your table, go for it. What else is there to say about that?
But...because, like the rest of us here at ENWorld, I'm overly verbose and opinionated, one thing to keep in mind is that each of the ability scores is a gestalt of different qualities, and sometimes things aren't directly related. For instance, DEX includes both hand-eye coordination and agility - two qualities that don't always correlate in actual individuals. Look at many baseball players: big, slow dudes with incredible hand-eye coordination. David Ortiz or Frank Thomas, for example. Ted Williams is arguably the game's greatest hitter ever, which implies he had some of the most incredible hand-eye coordination in modern history, and he wasn't exactly fleet of foot.
And a further point: ability scores are just that: abilities. I used to think they were wrongly named and should, instead, be called "attributes." But the high STR halfling supports the word "ability": STR isn't simply raw physical power, but the ability to utilize physical force with control and focus. Now obviously it doesn't make sense to have a low STR character be a big, hulking dude; but there is some play: you could have a 16 STR body builder who is a bit awkward and an 18 STR wiry halfling who is very athletic and has incredible muscle control.
I think someone up-thread made a good suggestion, that it is up to a player to decide what their ability scores mean. So a character with a high CHA can decide how that works: whether they are beautiful and know how to use it, or plain looking but with a strong presence, or any variation. But to say that CHA must include beauty ignores the reality of charismatic individuals in human history, and the lack of charisma that some beautiful people have. We can call this the "Adolf Hitler - Megan Fox Quandary." In same cases, physical attractiveness can be off-putting, if the person is arrogant, indifferent, etc. Or sometimes someone is incredibly beautiful, but lacks a force of presence.