It might be better to have a series of "quick lines" outside the building. You put on a harness, hook onto the cable, and slide down. It would need a braking system, but it might be easier and safer for physically challenged persons.
Interesting thought. I'm mechanically impaired but something could be invented. What about bungi-type stuff . . . modified somehow to meet a different need.
Actually, a home inventor could build something like you suggest. It would have some kind of built-in braking system, hopefully simple, and a harness like you suggest made out of narrow nylon stuff. You might be able to ratchet your self down somehow.