Well here are my ideas. For the story the Saints use the time machine to go back in time and kill Zinyak before the Zin invasion even begins thus saving the world. However this creates another reality where the Saints were betrayed by Ultor, Monica Hughes becomes the president instead of the Boss and revives STAG, some of the Saint lieutenats that died are still alive and six new gangs control Stilwater and a heavily modified Steelport. (If you're wondering how it works there would be three gangs in Stilwater and three gangs in Steelport). In terms of gameplay it would be similar to SR3, with the character customization of SR2 and an improve weapon custimization feature. For activities I think they should bring back FUZZ, Septic Avenger, Mayhem (normal, tank and mech), Fight Club, Heli Assault, Hitman, Chopshop and either Saints of Rage or Zombie Uprising. Finally as a bonus for completing the game you can use the powers from SR4 via a toggeble upgrade