I'm all for Lando dying, but I really don't think it would add much to any dramatic tension or give a bittersweet ending. Kill the whole fleet off if you want that. Get rid of the Ewok celebration and have the survivors quietly limp off home.

You really need to toy with one of the core plots a bit more to give it a bittersweet sort of finale. I liked the idea of Luke burying his lightsabre, and quitting as a Jedi. He would realise that the galaxy is better off without the Jedi now that the Sith are gone.