Okay, so I kind of have a Heathers AU of Six mapped out in my brain... it would be called "The Catherines"

Catherine of Aragon: Heather Chandler

Catherine Parr: Heather Duke

Katherine Howard: Heather McNamara

Anne Boleyn: Veronica

Jane Seymour: Martha

Henry: J.D. 

EDIT: Anna of Cleves: Ms. Flemming