> Russian law would give this pretext. Putin would be obligated by the constitution to protect "Russians" abroad. Ukraine has a huge Russian minority.

Russian law is not recognized outside of Russia. Besides, that logic would give him legal authority to conquer half of Eastern Europe.

> Ukraine is currently on the level of a 3rd world country. Russia would have air superiority within 24 hours

Do you have any idea what occupation means? It's soldiers, hundreds of thousands of them, and money/supplies to remain for years. Russia's economy is in decline, their armed forces are already deployed and stretched around the world.

This isn't a video game.