Yes, newer starlets like Miley Cyrus and Lady Gaga should aspire to follow similar paths to permanence like Margaret Cho, because if they don't establish themselves in a multitude of genres, they will be short lived. Most of the lasting music artists show off how truly talented they are, rather than just singing along with highly modified track.
None of these women are exactly "starlets". Margaret Cho is predominantly a comedian and she writes her material. Lady Gaga, in my opinion, has more singing ability than Miley Cyrus and she is more "artsy". Miley Cyrus right now is a famous performer. She's more of a singer-actress, and she may or may not have any staying power. Of the three, I think Margaret Cho is the most talented but they aren't really similar.
These new stars do not need to follow any particular path, and really need to simply follow their dreams, and continue their careers the way that they want them to go. Just because someone ahead of you did something a certain way does not mean that you have to follow.
Margeret Cho is a great comedian and an OK TV star. However, her permanence is debatable. Miley Cyrus and Lady GaGa will only be remembered as pop star embarrassments in 10 years. People will hide their CD's at the bottom of the pile, or archive the mp3 file because they paid $15 on iTunes and can't bare to delete it. Margeret Cho will stand as influential for Asian lesbian comics, and few else. She is a niche comedian, and her niche is not large enough to call permanent.
I honestly don't believe you can call Miley Cyrus and Lady Gaga newer starlets compared to Margaret Cho. The first two are already far more famous than Margaret Cho has ever been, so they should not follow her path. In fact, the first two have far more experience in some of the same fields Margaret Cho works in.