I always wanted to see a musical about the Beat poets. But if that's too big of a subject, then maybe just Jack Kerouac or Allen Ginsberg.
I've also wanted to see a musical about Dorothy Parker and the Algonquin Table.
But in both cases, there would need to be a lyricist on the level of Sondheim. With these subjects, crap lyrics won't cut it.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.