Here's what I would like to see if the devs were to ever update the packs:
Expansion Packs
Get to Work: Updated Aliens, more powers/technology/their own home world that wasn't one secret lot (maybe 3-5 lots)
Get Together: More icons for the clubs and the ability to create custom icons for them
City Living: Buildable apartments and the ability to live in apartments in any world
Cats & Dogs: The ability to take multiple dogs for a walk/jog at once
Seasons: Snow depth and more detailed visual effects similar to TS3
Get Famous: Singer and Modelling careers
Island Living: Two words: Scuba and diving/underwater gameplay. The mersims need a home!
Game Packs
Outdoor Retreat: Better hiking
Spa Day: The ability to do yoga/meditation anywhere without the animations being tied to a mat/meditation stool (similar to how yoga worked in TS2)
Dine Out: Working as the chef in your own resturant
Vampires: I wish the vamps were a little scarier maybe but I'm struggling to think what could be added gameplay wise (in other words great job, EA!)
Parenthood: I honestly believed we would have got an update to babies in the pre-pack patch so... actual baby Sims!
Jungle Adventure: I haven't play around with this pack much but I love the idea of more packs with this theme, more adventures and gamepacks with a high chance of death! There are actually quite a few unique animations/interactions, too!
StrangerVille: For what it is I actually really like this pack! I would have liked the story to have gone on a little longer/more complexity and developed a bit more of a back story for why mother was brought to SimNation in the first place... but I suppose that is up to the player's imagination!
Stuff Packs
Luxury Party Stuff: More high heels/nail accessories/better male hairs and clothing
Perfect Patio Stuff: In-ground hot tubs!!
Cool Kitchen Stuff: More styles of kitchens!!!1!!one!
Spooky Stuff: To have been saved for Seasons content
Movie Hangout Stuff: An actual working cinema venue/made into a gamepack instead (with developed gameplay)
Romantic Garden Stuff: Improved romantic interactions e.g. seated proposals
Kids Room Stuff: The ability for teens and adults to play/collect voidcritter cards!!
Backyard Stuff: Pool accessories/items
Vintage Glamour Stuff: I really liked the 2-tile bar with no drink making animations - honestly, my sims would make more drinks if I didn't have to sit through that ridiculously long drink making animation (as beautifully made as they are!)
Bowling Night Stuff: The ability to have bowling alleys and resturants on the same lot
Fitness Stuff: Free-weights etc., more items that weren't reskins of previous items from previous packs
Toddler Stuff: More hairstyles (come to think of it more toddler CAS items in general!)
Laundry Day Stuff: I wouldn't touch this one! Does what it says on the tin
My First Pet Stuff: I wouldn't touch this one either - but not in a good way :D no but seriously I think more types of first pet e.g. chameleons, turtles, lizards, rabbits etc.