I thought a lot about a similar concept, using drones (maybe even swarms). Has this ever been attempted? I guess the energy and posioning constraints would be much tighter, but it would make for a fun project.

One advantage I see to using strings and wheels is that there is no strict requirement for spray painting, as it can be done with regular rolls. I was a bit disappointed to see that it used spray painting here as well (and quite a bit of sprays bottles per painting).