I understand your point. As a disabled player I've been in 2 minds about this for a long time and I've said this before. My problem is how different conditions could be attributed to Sims without moodlets being too overwhelming for the game.
I welcome all of the diversity that's being added to the game, I'm happy to see it and there is a little twinge I feel seeing all the inclusion and thinking, but I can't make my best friend who is in a wheelchair or the little ones I am close to who are autistic or my own disabilities (which logistically would be a real difficulty to show a curved spine). If I were to create a character with any of these traits, if it were possible I don't think they could get the impact right.
I mean, as an example when my Sims travel I get a homesick moodlet stuck for days which hampers gameplay. It's still there when they get home. If my Sim is an animal lover they get the Missing Furry Friends moodlet stuck even when they are with their animals. So my fear is that if they do finally add Sims like me, the moodlets will be a real problem. In my game, they already are.
I also see the massive amount of glitches with the medical career, in my game it's virtually unplayable. So with all of these potential game breakers I just don't see how they could do it. Yet at the same time as we gladly welcome so much diversity and progression into our game it does leave us with a missing piece.
I just think in order to do it, they need to fix more for starters and sadly (I'm usually more positive so bear with me, this update has really kicked me in the teeth) this new update has shown they are not going to fix enough of what is broken.