I haven't seen any of the R Musicals listed either! I have to say, I think Rocky, the Musical would be interesting to see. Or especially a French musical of Romeo and Juliet? YES PLEASE. Assuming you speak French, that is. Which I used to but don't remember much anymore...ahem.
Let's go with Rocky.
Rocky singing and dancing while fighting? There have been stranger things, I suppose! I really love what they said in this brief commentary (and the music doesn't sound too shabby, either!), about what Rocky accomplished by putting his mind to it. How the fight isn't what's most important, but the heart of the story is.