I wanted to jump in on this thread as I had the same question about how long the staircase can extend before running into walls, doors, or hallways.
Are the new stairs permanent? I know a senior who uses a flat brick when she visits her friends who have stairs. The brick is moved one step at a time as she climbs. Obviously a tedious and possibly hazardous maneuver. I f your stairs can be adapted to be movable and repositionable perhaps a three to four step at a time solution can be achieved for those who don't have the room to expand the stairs.
Just a thought. Overall, I agree with Robert, you seem to have a lot of this covered.
One of the Seniors I worked with for this challenge brought up the issue if ill-fitting shoes. Not only are they uncomfortable, but can pose serious dangers. I'm glad to see you tackling this problem and the various areas you are trying to address. I would like to suggest one more addition: Adjustability and reconfiguration. I learned that one particular problem seniors have with their feet, is that various medical conditions and poor circulation can cause their feet to swell considerably over the course of a day, and sometimes in mere hours. A shoe that fit fine at 9 am, may become too tight by noon and then too loose by evening. Is there a way to incorporate a dynamic and easy method of adjusting the shoe as the user's feet shrink and swell throughout the day? I would love to see your ideas on that.
I like the design and feel it is very well suited for the purpose you are intending for. Looking through some of the responses and feedback, I agree that a ratcheting system with a fall break mechanism incorporated would be two good additions to the design. I a thought about how to return the bar to either end of the staircase: a hand crank or motorized crank that can be used to summon or send away the bar. That way regardless of who used it last, there is always a way to bring it the end of the stairs where it is needed.
Another thought was to incorporate vertical elements that act as a gate of sorts. In the event of a fall, the user may not have the reflexes or strength to catch themselves on the bar and could easily slip under the bar and down the stairs. Perhaps there is a way to adapt this fence to follow behind when climbing the stairs.