In This Scenario, Napoleon never returns to France, instead, he just, somehow, stays on Elba until he dies, his son becomes emperor of the island, and then his son, until today. Elba today is a constitutional monarchy. Due to its iron resources, it has become a moderately rich national, though it has been involved in both world wars.
In 1814, Napoleon decides to stay on Elba for the rest of his life, he vastly improves the lives of the people of Elba, trying to improve the island's wealth, prosperity and infrastructure. The usual line of succession continues and nothing changes, in 1861 Elba Denies Joining the Italian nation. in 1890, Elba Joins the Allies in fear that Italy, (which is part of the Entente) Might try to conquer it if a major war breaks out. This will change the island Forever.
World War One
In 1914, Upon the outbreak of World War One, Elba joins the war after being circled by the Austro-Hungarian Navy multiple times, the Austrians Invade and occupy the Island. When Italy joins the war, the island is not a big deal, but a goal to liberate in time, eventually, the Italians attempt to liberate the island eight Times during the war, 70,000 Deaths in total, until the Italians liberate the island.
Elba was COMPLETELY destroyed by World War One, New Paris, its largest city, was completely destroyed, 75% of the City had to be rebuilt, the task was met, though. The Allies helped rebuild and the island reached prosperity never seen before. What would come would be worse.
World War Two
In 1939, Elbans, remembering the Horrors of World war one, declare neutrality until May 1940, When Italy joins the war and attacks the island, right before the attack, all Elbans were evacuated, knowing they would be mass slaughtered, the island was deserted, And the Italians marched in. In Churchill's plan to punch the soft underbelly of Hitler the island is liberated, it is, again, completely destroyed, as Italian resistance is very fierce.
Post War and the Cold war
After World War Two, for some reason, the soviets gain control of the island, and set up a communist government on Elba, The Peoples Democratic Republic of Elba. The Soviets rebuild it. In 1972, However, The people Overthrow the Government, Soviet leader Brezhnev Plans to Invade the Rebellious Island, But Before he can, it joins NATO. Brezhnev realizes that invading it would mean World War III, So he lets the island go. It has a population boom, the population grows to 130,000 with some of the highest density on the planet. It has an economy boom, and now, the island's prosperity has reached its highest ever, it has the second kighest standard of Living on the planet.
After the Cold war, the country's path is lost. It doesn't know what to do, but maintains rich and prosperous. Until 2000, when it was hit by a 6.5 Magnitude earthquake, it destroys everything on the island, the devastation is worse than the Haiti earthquake, it recovers rather quick though, and the government handles the situation VERY well. It joins the War on terror, Most people, to this day, still support the decision. it has not joined the EU. Due to Elba being an island, it is a hotspot for Refugees From The Middle East to come, However, it will Deport and Deny ANY, Migrant, Gaining Heavy criticism from The EU, Calling it a human rights violation.
Yet the island is still a leader in human rights, it is the only country to still use the Lira after Italy dropped it. Tourism has become a large sector in the economy but 74.2% percent of the country's GDP is industry still due to its iron resources and its rebuilding after WWII under the Marshall Plan.