Those are some very interesting alternative endings! I think I would have enjoyed any of them, but I think the most fitting alternative would have been for Frodo to fall in himself. It would be terribly sad, and so would have made for a great emotional ending.
Also, ever since my sister saw the last movie, she has thought that a great ending would have been for Sam to die by taking the ring from Frodo when he realises he won't throw it in, and falls or jumps into Mount Doom himself. After everything Sam and Frodo have gone through, it makes sense that he would have died to save Frodo and the rest of Middle-Earth. But I would have cried
so much!
