With current NPC interaction it's pointless to suggest something about sex appeal, if only it won't affect combat, later it may work like in original Fallout, opposite sex NPCs will like you more and the same sex won't, nothing complex. In example, you're 1 CH ugly powerbuild, you will have no possibilities to advance in some faction ranks / stroly line / whatever they will implement, sex appeal may affect your CH by giving floating bonus against same sex and penalty with opposite, but if only your CH isn't 1 already, etc.
Right now it can be used only in combat. Also forget about dialogues, you can read them only in special created locations where you're alone and know that noone will ever attack you, I still never ever read what Metzger, Little Jesus, etc are saying, because I'm not going to read whole dialogue in unguarded town with a risk to lose quest item, so all NPC interactions is pressing "1", "2" etc. buttons and reading wiki to see where you need to go and what you need to do.
About this is not "trait", you forgot to add penalties!! Trait must have something bad! Who cares? If you're picking a trait, it means you already not going to use whichever penalty it'll give. Even when there will be more dialogues (and in safe places or alteast without permalosing quest items) wich are affecting your gameplay, everyone will know what they need, if they'll need to have high BoS rank and that guy who promotes them is a male, then they will make female with this trait, etc. so it will work like fast shot, if you're not going to do aimed shots it's not a trait for you, or small frame, if you're not crafter/looter, then it's not a trait for you, good natured, if you're not troll build with sg+bg+unarmed, this isn't a trait for you, etc so why sex appeal should have a penalty? Of course it should, but people will avoid it anyway. Btw it already have a penalty, it takes you 1 trait slot, so you'll have only one more trait, so you can't have good natured AND small frame, my suggestion: remove all damned penalties! Anyway everyone are taking 2 traits, sometimes you even want to take 3rd trait, but you can't, probably there must be some bonus if you don't have traits at all or have only 1 trait.