His life’s story would have been a heroic epic rather than an epic tragedy….
As to what would have happened after his death, I see 3 possible political consequences with just one ending.
A coup takes place in Paris, much like the Malet conspiracy. Loyalty to Napoleon’s family and his heir is practically non-existent. The empire is overthrown and the republic restored. Bourbons are not recalled.
Napoleon II is proclaimed Emperor and a regency takes over until his majority. Marie-Louise is regent, strongly counselled by French politicians and marshals and influenced by her father, Emperor Francis.
Marshals and politicians scramble for power, possibly with bloodshed. Eventually, a strong leader emerges, mostly likely a marshal, and he takes over as new Emperor.
Whatever the exact scenario, in each case the French withdraw to France if offered reasonable terms to end the Franco-Russian war, perhaps mediated by Austria. It was Napoleon’s monumental ego and ambitions that led to the war and without Napoleon, France would not have felt the same need to dominate Russia and the rest of Europe. Without Napoleon’s constant bullying, the other European powers wouldn’t be as hostile and a powerful France would be accommodated as other temporarily dominant powers had been accommodated before.