YES YES YES ! We definitely need L shaped, and more flexibly designable staircases. The staircases we have now are very obnoxious, looks extremely ugly for middle and highest wall setting, they take a lot of space, not practical.
Also a possible new stairs update can come with some "indoor platform" feature to the game. Those platforms can work like foundations with a height slider, but independent from the actual foundation. That would help a lot for being able create unique staircases depending on the builders imagination.
We also need multiple wall and foundation heights within the same floor level.
Terrain tools. (like in ts2 and 3) and constrainfloorelevation cheat with that of course.
Some curved walls around some magestic spiral stairs....
And Inward curves for decks. When you build a round deck, it can only be curved outwards, but you can't add any inward curving deck next to it i.e. if you want to create an S shaped design with those decks.
Such limitations have always been problem for us sims builders ever since the very beginning. In ts1, ts2 days, that was normal, graphics technology were yet still developing but now in 2017 possibilities are almost endless. I believe they can just do it if they wanted to. Keeping some things simpler than it is necessary doesn't work well imo.
Plus, while even some random player who is sitting at their home, can create a mod that includes new sim movement animations, (yes I'm talking about the deadly toddlers mod) Shows that EA can actually do A LOT more for TS4.
And as we have given up open world just for the sake of slow computers being able to run the game, we deserve more sophisticated features that previous games didn't have.
From TS1 to 2, it was a huge step forward, we've got a truly improved, renovated gameplay. Since then, on TS3 and 4, nothing really changed much in terms of game mechanics, features besides visual quality. I think it's time for some really new features. More flexibility, less limitations. Especially for build mode.
Or maybe I just just hope for a second TS revolution for TS5...