One thing I really want in TS4 is more venues to go to.
An arcade GP, with arcade machines, claw machines, whack a gnome, shuffle tables, hockey etc, earning tickets by achieving high scores on the machines and redeeming them for exclusive prises (similar to festivals on TS1 and TS3), would be super awesome to get.
A funhouse/amusement park GP would also be very interesting. It could feature a mimes or acrobat NPC's, fun house mirrors, carousels, cotton candy machines/vendors, magicians that pull things out of their hats or do card tricks, inflatable houses for kids, making balloon animals, and so on.
An asian sort of vacation spot like Takemizu Village, would also be something wonderful to have. With a teppanyaki grill/restaurants, sushi, martial arts skill, dojo venue, inn's for sims to stay at, etc.