Blockade and force Coruscant into a siege. The rebels would be desperate for this to happen, as since ESB they have been aggressively pursued and chased around the galaxy and are willing to launch a risky attack on the imperial center. They are losing the war, a second DS is being built, and they need a decisive victory now to turn the tide of the war before it is finished. Time is running out!
The idea for Endor would be it's been a symbol of nature and peace for thousands of years but overpopulation on Coruscant is forcing the empire to clear it for settlement.
So, you can put some of those big Avatar front loaders knocking down trees and so forth. You could even edit in some of those shots of that huge open mine on Pandora as the spaceship flies over. This would be a quick visual example of how the empire is transforming the landscape. The human Pandoran base could become the generator base.
