1. More gameplay options, on the level of the MC Command Center mod. It's not like giving people the ability to tweak things like population settings and alien abduction rates themselves is going to kill the game. In fact, it makes it better.
2. Fix the emotions system. That means removing the ambient Happy moodlets from furniture and decor, making Uncomfortable boost negative moods, adding Scared as a mood in this game (using Tense for Scared is just plain foolish), adding a Stoic trait that gives your sim a permanent +2 or +3 Fine moodlet that makes it harder for other emotions to become the dominant one, and fixing certain moodlets to make more sense (change the moodlet for having low fun from Tense to Bored, change the moodlet from trying for a baby on a lot with the Dark Ley Line trait from Energized to Uncomfortable, etc.). The emotions system is really unbalanced right now, and just relying on mods (which can be broken by official updates) just doesn't cut it.
3. Add an official custom content creator extension. TS2 had BodyShop and HomeCrafter, TS3 had CASt, TS4 has...a third-party app that we have to closely monitor and update by hand. If they won't give us CASt again, the least they could do is give us an official CC creation tool like they did with TS2. You know, something that allows us to make our own eyes, hair colors, and skintones, as well as retexture existing items and clothing to our heart's content and make our own wall and floor textures...maybe even edit meshes directly in the program and/or import new ones and paint textures directly onto those meshes right there in the program. It could be revolutionary!
The runner up on my list is:
Checklist Free Functional Community Lots/Community Lot Expert Mode. The checklists for building community lots are too restrictive, and if I want to build anything original I have to use the General lot type, which does not attract NPC sims at all, leaving the place a freaking ghost town. I want a checklist free, expert mode community lot that functions like a community lot: NPC's visit and use the facilities, period. If there's a chess table, they will just use it because it's there. If there's a bar, a bar tender will show up and NPC's will order drinks, because it's there. If there's a T.V., NPC's will watch it...just because it's there. You know, like how community lots in TS2 worked. You could build a community lot that was nothing but a bathroom and 20 chess tables and some chairs, and sims would come and use it. TS4, the supposedly more advanced game, not being able to pull that off is just plain bogus!
