I'm running into this in my story - big ideas but I can't realistically control a household of more than 3-4 sims at once. Right now I've got several households running, rotating between them and/or moving sims between them as needed. I keep running into problems where, narratively, I want members of three households together in one scene but it's impossible to coordinate.
Edit - one trick I did figure out, with my teenage werewolves... I'm using LittleMsSam's Choose your Roommate mod and I have the teens as the sims and the adults (in this case Kristopher and Lily) as "roommates." That way they're in the household but I don't have to deal with controlling them.