Other than open world and color wheel I don't believe there's a lot the developers can't do in this game.
On different heights for the sims.
https://twitter.com/SimGuruGrant/status/1075817796401913856
On bunk beds and spiral staircases.
https://twitter.com/SimGuruGrant/status/1075187578607853568
I don't think we'll see different heights in the game because of the prohibitive cost of making all new animations for a new height. And new clothing.
I do believe we'll eventually get bunk beds and spiral stairs. You just gotta believe. :)