Hi, Cheshire Figment!
I know that there are a couple of books written about this very topic, but of course I no longer remember the titles. A dear friend of mine has muscular dystrophy and she and her husband built an accessible house. Now we'll see how much I remember about the design(smile).
All one level for entry. The front sidewalk goes directly to the door with only a lowered door jamb to get over. And the door is wide enough for a wheelchair, with a lowered peephole and levers and electronic lock with large buttons on the keypad. It is also one level from the garage into the house and the same kinds of doors. The laundry room is directly off of the main bathroom and she has front loading washer and dryer. The bathroom also has a floor drain in the center, a roll-in shower and a jacuzzi that has a swing door to get in (when closed it is water tight) and a large plastic molded seat to sit on. She can roll with her shower chair right into the jacuzzi, transfer to the plastic seat, close the door and fill it up. All she has to do is drain it and transfer back out. Regular raised toilet with grab bars and the sink is cut out so that the wheelchair can slide under it, with the outlets located on the outside of the sink cabinet near the counter.
All of the hallways are wide enough to handle not just a wheelchair, but a longer length wheelchair for when she will need a respirator with her. The halls look extraordinarily wide, but this is necessary to handle the turning radius. She has handrails in the hallway, but those can be removed if necessary. All of the light switches are easily reachable from the chair as are all of the outlets (higher outlets, lower switches), the shades are remote controlled (the automatic motorized ones) and the deck is also zero entry with a special set of patio doors that eliminate most of the hump. If I remember correctly, the door jamb of those is set almost exactly even with the floor and so she can roll in and out with no problem. That door has an automatic opener on it (swings out). There is a ramp leading down from the deck to her raised bed gardens and the pathway is paved.
The kitchen counters are lowered with an open area under the island in the middle (which has a small sink) so that she didn't need to leave it open under the main kitchen sink. All of the switches for everything are mounted on the edge of the counter not up on the walls. Their are no cabinets. Well, there are cabinet doors, but when you open the doors there are large pull out drawers that hold everything in there. The main kitchen sink has the faucet on the side and not at the back and the faucet operates with a lever. The stove has all of it's buttons on the front of the stove and she has an eye level (from the wheelchair) wall oven with the buttons mounted at the bottom not the top.
Well, that's about all I can remember(smile). Hope it is useful!