Related to window-washing is building-washing. My brother-in-law used to work at his father's building-cleaning company. They do the same sort of thing, hanging off the side of a building to refurbish the concrete and such, but they've got a lot more equipment.
You should find a window-washer to talk to; I imagine they've got some pretty good horror stories about being pushed all over the place when the wind blows. I know my brother-in-law has some doozies.
Okay, here's the hidden project: antique systems vs. modern systems. The window washer you saw versus the machines that they use to wash the windows on, say, the Sears Tower. I think the key to making it something other than hackneyed would have to be ensuring that the "primitive" systems are still viable and used: you NEED your windows washed, and soap and water are pretty much to only way to do it. A shot of an old telephone operator console from the 1940's next to a modern PBX wouldn't cut it, for example. Nor would auto-plant assembly-line robots and auto-plant assembly-line humans. A compass vs. a GPS unit, maybe? A spirit level vs. a laser level?
Interesting idea. I think I'd rather (as if I'm planning to run out and do this) focus on the antique systems in and of themselves, instead of comparing them to modern systems -- too much temptation to apply a John Henry-esque structure to the project, I think.