I think one great addition that SDS could add to RTTS is including the customization of player traits, such as hitter tendencies and splits against RHP and LHP.
Selecting pull/balance/push could add a new level of dynamic to hitting and also free agency. An example being the Yankees could show more interest in free agents (RTTS player) who are lefty pull hitters or oppo-hitting righties, since their stadium plays to that.
Splits against right/left pitchers means the caps would be lower than the default value. Say a right-handed batter has better splits against LHP, then caps for vs RHP would be lower to start with.
I find it naturally difficult to hit to certain hitter tendencies or dominate one type of-handed pitcher vs another, and I think these additions could add a specific new flavor to RTTS.