“My Dystopian Robot Girlfiend”, while still in the 0.90.xx development stage, is set up for modding and hasn’t (to my knowledge) received one in ~this website’s oeuvre~. There’d be a pretty wide range of options that wouldn’t have to involve tweaking the existing plot, from just making the titular character chubby to incorporating morphological changes over time (there’s already a cooking game and an income/food economy, just aimed at PC stat buffs at the moment, that could be exploited).
Another thing that sounds easy but would probably be a nightmare to execute properly.