3. Retconning/Retreading. Since Lelouch S2 was clearly designed to be the end of the series, they quite quickly tied off most of the loose ends. In order to start this new season they will have to untie those ends or retcon certain things to make t fit. More importantly though, the show completed it's themes, told it's message and ended it's story. To reopen it and keep it as a Code Geass show without retreading on the themes/story beats which have already been completed will be extremely hard since they are still using the same cast with the same character dynamics.