There's a handful of mods out there available for Castaway Stories, but the best thing to do is not to put any in until after you complete both stories and get Free Play Mode to play the game.
The motives decay a bit faster for a reason, and it is related to the stories to help you get through the stories slightly faster by sending the Sim to bed and speeding through to the morning.
Carrigon at her
site has several mods that sounded like what you're looking for.