Hotels, resorts, banking system, owning more properties & house builders adds huge amount gameplay!
Simmers have said for a long time that money in the Sims is too easy to get and then you have nothing to do. That could be remedied. New banking system with loans House Builder career teller, ...
I second the addition of hotels! KawaiiStacie has a resort and hotel mod it would be mad awesome if you could somehow take that and integrate it into the main game with credit giving to her of course.