Oh gosh ditto on the handicapped/disabled sims!!! It's shocking to me that such an inclusive game doesn't have any sort of options for disabled sims. Things like wheelchairs and crutches (chairs and crutches like the ones people actually use long-term not just the ones hospitals give out when you've injured yourself), prosthetics, hearing aids, seeing canes, oxygen tubes, etc. You could even have scales of expensive aids like a cheap basic wheelchair or a more expensive powered chair. Like Brian mentioned, you could combine with Cats and Dogs for service animals. I understand that this is a very complicated thing to implement and needs to be done carefully and thoughtfully but I think it could really really add to the gameplay. There is some cc for accessibility cas stuff which is nice but it is often buggy and isn't the same as having gameplay options.
A true inclusion of disabled sims would probably require all community lots to be updated to be accessible (so many of them have things like bathrooms on the second floor with no elevators and absolutely nowhere has ramps) but maybe you could even bring that into the gameplay like eco-lifestyle where your sims can get measures passed that require old buildings to get retrofitted to be accessible. You could add an "Accessible" lot trait that could give your disabled sims positive buffs or increase their movement speed.
I understand that the type of gameplay changes I'm proposing here are more similar in scale to an expansion pack but I really think that if at all possible it should be a base game update. It would suck so much for disabled simmers to have to pay extra to feel represented in-game while most everyone else can just have the base game.
Also imo this update Should Not be combined with a mental health update (which is by itself also probably a good thing). Discussions of mental disabilities often get brought up as a response to discussions of physical disabilities when really they should both be discussed as important topics without infringing on the other's space. I am worried that a combined physical and mental disability update would mean that the stuff for physically disabled sims gets overshadowed by the gameplay changes for mentally disabled sims or visa versa. It would be really sad to get an update with a bunch of gameplay for depression and dyslexia etc but just like one wheelchair and that's it. I'm hoping that makes sense, I've just seen it happen before with disability discussions and it sucks.
Anyways I know this would be a really large update and a huge undertaking for you guys but I think it would make a lot of people really happy and add a new interesting dimension to the game. It would likely take a long time to code (who knows maybe you're already working on it??), but July is disability pride month in the US and maybe you could aim for a July 2021 pride release???? idk just a thought.