Representation

While the idea is interesting (I'm on the spectrum myself), I have to say one thing: how to better represent the spectrum? No two autistic people are the same, each have different stims, different disturbance makers, different special interests (though The Sims does tend to be one of the popular ones...) etc.

It's difficult to get right. And according to one article, Socially Awkward trait from High School Years is one of the ways they have represented neurodiversity in The Sims 4 (yes, it exists in The Sims 3, but it also boost Science skill gain though...).

While I understand where you're coming from I think it would be really difficult to truly give Sims the full spectrum of autism. And what about other mental challenges like MPD or BPD? Depression? Sociopathy? And while I wouldn't mind seeing Sims in wheelchairs the last thing I want to see is an incontinent Sim. The Sims, while a "slice of life" game, isn't meant to cover everything in real life. It's a charming and whimsical (and rather whacky) escape from real life and its struggles. I think the things you ask for are better addressed by mods and should not be imposed by default on everyone's game.

Even if they created the ability and covered some areas for people like me (who have AUADHD), like an emotion for being overwhelmed or, as HelloMiakoda said, adding stimming to interactions, just making some form of effort is all we're asking for. I'm not saying force it on everyone; allowing it to be an option we can add and remove would be the preferred way to go about this.

Being Autistic on the low end of the spectrum, there is a way to make your Sims autistic and on a low end of the spectrum and that is when you create your Sim look for one: Loner and two: Social Awkwardness and something else I can't remember what is was. 

I've been asking for a Disability pack that covers: wheelchairs, prosthetics arms, hands, legs and feet for awhile now.