Control one sim and don't switch to any of the others? That's what people who play ISBI-style legacies and the asylum challenge do... I do it all the time, actually. No need for a mod, either

Make sure free will is turned on for the lot, control only one sim and away you go.
Alternatively, turn on debug mode then shift click on each sim on the lot and select Make Unselectable. Family members will remain on the lot but you won't be able to control them because their portraits will disappear from the panel. This is also often used by ISBI and asylum players so that they are not tempted to control the "uncontrollable" sims on the lot. Again, no need for a mod. The sims should reset back to controllable when you re-enter the game next time you play.