This is basically an AU where the Mane 6 are actually famous Musical Stars, But since I only know about a few people, I'll need more people to suggest who should represent each of the Mane 6.
Twilight-Michael Jackson
Spike- Janet Jackson
Pinkie Pie- "Weird Al" Yankovic
Rarity- Beyoncé
Fluttershy-
RD- Britney Spears
AJ-Gretchen Wilson

If you have any suggestions, please leave them in the comments because I can't do Chapter 2 without the full Cast.
(Note: People who you suggest need to have a SIMILAR, BUT NOT EXACT personality to the pony they represent)