re: So if Napoleon wins Waterloo, does it merely prolong the inevitable?

Also why Arthur Wellesley, Duke of Wellington is not mentioned with the greats is almost criminal. The man never lost a face to face battle. Maybe you could say Burgess, but that was more a strategic retreat... why waste time and resources on a siege that in the end doesn't gain you much .....if anything

I don't know that Waterloo was at all a winnable battle for Napoleon. Even if the battle had lasted for more than one day, by the next morning, Napoleon's reinforcements would not have been there.

Grouchy's force might have been able to fight its way to the Waterloo battlefield by noon the next day, but, not before, I think. Grouchy had a lot of Prussians between himself and Napoleon on both June 18 and June 19.

There were many hundreds of thousands of British, Austrian, Prussian and Russians advancing on Paris on 18 June 1815. Merely surviving after the Waterloo Battle would just prolong the inevitable.

In the 100 Days Campaign, Nappy needed to destroy the enemy armies in detail, that is to say, one at a time. He had an opportunity to destroy the Prussian Army at Ligny, but, D'Erlon's First Corps failed to appear at all. It's prompt intervention at the right moment would have destroyed the Prussian Army and chased remnants out of Belgium. Then Nappy could have begun operations against Wellington and tried to defeat him before the Russian and Austrian Armies arrived.

Even if Nappy could have chased Wellington back to Britain, the Russian and Austrian armies were still approaching. I doubt that Nappy could have beaten them both, too.