First off, you need to define "flop."
My first thought was SEUSSICAL. But after its Broadway turn, Cathy Rigby tweaked and redid chunks of the show and the 1st Nat'l Tour was SUPERB!!! Then the non-Equity tour occurred and went back to the original Broadway script but completely re-staged it. BUT it's not really a flop because it's one of the most popular regional titles performed today. Still, I would love to see a complete revisioning and reworking, moreso than what Rigby had done, and brought back to Broadway.
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle