How about a base Charisma score of 14 or 16 as a pre-requisite? Maybe a certain number of ranks in a specific skill? I could also see the template helping out with Bardic music.And with regards to Succubus being a template, that could actually be a cool change. Who doesn't like being able to add Cha boosts and ability's too a race described as being beautiful or Charismatic anyway? Gives you something to Enhance flavor.