I’m sure they could be repurposed the way you suggest. But don’t most people in open spaces use slack or equivalent for that?
Surrounding yourself by whiteboards might also allow you to approximate walls.
I've got two colleagues that are horrible about this. Fortunate enough to have an office with a door, and play music quietly at my desk so I'll hear it if someone knocks--since I face slightly away from the door.
Except they'll skip knocking and just walk in and around my desk to do the shoulder tap if the door's open.
I've been training them out of this behavior by saying "oh hey did you knock? I must have missed it, what's up?"
Time will tell how this goes, heh.
Although I do wear headphones pretty much constantly, I have always made a point to be responsive to people and not ignore them. If someone needs my attention, they will get it, and I made a point of doing everything I can to help people. Yes, I'd rather not be disturbed, but if they really need my help, then I will gladly stop and help. This is no different than if I were in a cubicle or my own office. I have no problems with that kind of distraction. It's the unintentional distractions that we need to eliminate.