What if he never meant insane? I'm meaning a Simon who simply didn't go on the plane to get that crown, and went into a vault. A non-crowned Simon, however going mad due to leaving his dearly loved fiance' behind.
Quite fun actually. Simon slowly falling into his own crown of guilt and shame, which basically turns him into an Ice King. Time goes on, his hair grows longer and white and a beard is in place. Ta-da, you have the Ice King!
Yes! The characters are perfect! Finn as the lonely badass Courier who has no idea how he got where he got, Jake as Boone, PB as a Brotherhood of Steel paladin (SCIENCE YES), and Marcy as Cassie the drunk who lost everything to some competitive caravan company!