This sounds like a great idea for people who are not able to stay at home and receive the level of care that they need from their family, or for single people who have no extended family in the immediate area. Many PALS' first choice, though, would be to stay in their own home and to develop care accommodations there. It sounds like you are planning to make this more like a home away from home, which is good.
Some ideas I have....wide hallways and big enough spaces in living and dining areas to allow people in electronic wheelchairs to maneuver and hang out together. In general, there will need to be space in common areas for and organization around the wide variety of each person's assistive equipment, of which there will be a lot. You wouldn't want to have to hang out in your bedroom access the cough assist machine or Bi-pap and get isolated. The kitchen will need more than one cooking area to take care of many different dietary needs, including boiling PEG tube feeding equipment, blending foods for those who cannot eat solid food, and cooking regular meals for those who can still eat them. Even with all that, people need a sense of community while having meals and to be able to sit around a table with companions. More than one bathroom, maybe even three. Bathrooms will need a lot of research on your part to have all the equipment that is needed, bath sliders, lifts, bidet toilets, etc. for people to maintain as much independence for as long as possible and then get help with dignity, not awkward arrangements. You also need computers available, either in the private rooms or in a computer room with one for everybody, as the computer is many people's way of communicating and remaining part of the wider world, and some even do artwork or write books on them. Outside the home, a beautiful garden with tall raised beds that people can reach if they are still able or at least see easily to enjoy. Also, lots of benches with backs for people who are still somewhat mobile to wheel their walkers to and sit to rest as they walk around. Well, I suppose now I'm dreaming if you are doing this right in the city.
Anyway.....Lots of windows to see out at the garden and the trees and sky, and of course, all on one level and with ramps as necessary....and a wheelchair lift van to get people to and from appointments and go places.