And, on the principle of making lemonade out of lemons, have you ever considered installing an external lift (like these) which would make the whole block more accessible? It may not be possible but if you have a stairwell with one wall facing the outside of the building it would add value to all the units on the first floor and above.
I’m sure stairlift guy would be happy to contribute and, given your previously mentioned hassles with getting furniture in and out, your neighbours may be happy to pay too. Just a thought.