Enter “& Juliet,” a savvy if stunningly unsubtle mashup of a musical from London that aims to redress that balance for Broadway fun and profit. This nonstop party-empowerment show gets its theme of feminist revisionist British history from “Six,” its Shakespearean humor from “Something Rotten,” its nonbinary savvy from “Head Over Heels,” and its collage-like spectacle from “Moulin Rouge.”