I always thought it would be interesting to have some kinda of multiple choice/outcomes strategy game where the campaign goes different turns depending on who is having an advantage. Would work well with a geopolitical show like Geass atleast.

>players can just follow the story and pick a side
>or they can attempt to change the outcome and get a different ending
Like the end of S1 where Lelouch is getting his plans fucked up with the kidnapping of Nunnally. Give the player the option to put some additional bodyguards next to her in order to prevent that from happening. How would the story play out if Lelouch won after S1?