I wonder if there would be a way to make a symbolic link on the server to point toward the other location and get the images to load from this spot instead.
This is one of those "off the reservation" configuration options that go outside of the standard structures and expectations set up by the open-source developers. I've learned the hard way to follow the examples of the defaults et al, which smooths transitions like the current upgrade from Joomla 3 to Joomla 4.