So checked on the level limits to answer the question.
Max Rank is PL+5
Max bonus from ability score is also PL+5
So just you'd be limited to 1 rank in bluff/diplomacy but you could have a high charisma bonus as well.
My main concern is people often put down crazy high attractive and then everyone reacts like it's no big deal. I consider "selling" (pro-wrestling jargon) other people's powers part of the roleplaying social contract, but I hate being the only one "selling" something because that makes my character look like an idiot which isn't fair to me.
Assuming your charisma is at least 16 (+3) those things I said would be true even untrained.
Compare to the equivalent bonus from the charisma scale
Attractive 1 - 18 highly gifted ie only a few in the US like a supermodel.
Attractive 2 - 26 Low Superhuman ie beauty slightly beyond what is humanly possible like a superhuman super model
Attractive 3 - 34 High Superhuman ie beauty of god of beauty or a powerful superhero who's power is beauty.
Attractive 4 - 42 Very High Superhuman ie rare beauty even among gods of beauty.
Attractive 5 - 50 Cosmic ie the cosmic entity embodying the concept of beauty.
I am fine with even the charisma 36 (+13) attractive 3 (+12) with a rank in diplomacy character. It's a perfectly fine shtick but to looking up the routine behavior for that shtick at that point is someone who wants you dead, talks to you for 6 seconds and decides to help you instead, and everyone else will take risks to help you after short interactions. And you've got a 35% chance someone who started out your friend will become an obsessive fanatic willing to die for you. If someone like that walks into the room and gets no reaction that's a "no-sell" type situation which I dislike.
Core Rules 2nd Edition: Hero creation: Power Level: page 24:
Skill Rank: A character cannot have more ranks in a skill than the campaign's power level +5. So in a PL10 campaign, a player character cannot have more than 15 ranks in any one skill (10 + 5).
Ability Scores: Ability scores are limited to a bonus no greater than the campaign's power level +5. Strength is restricted by the Save Difficulty limit to a bonus no higher than the campaign’s power level, as is Constitution by the maximum Toughness limit. This means a limit of (10 + twice power level) for Strength and Constitution and (20 + twice power level) for other ability scores. The Strength and Constitution limits may be raised with an attack/defense trade off (see the following section).
Core Rules 2nd Edition: Hero creation: Power Level: page 24:
ATTRACTIVE SKILL, RANKED
You're particularly attractive, giving you a +4 bonus per rank on Bluff and Diplomacy checks to deceive, seduce, or change the attitude of anyone who might find you appealing. This bonus cannot increase your total effective skill rank higher than the campaign's power level limit.