It still would be very productive, since you can install the gear in much more accessible location
But the wiring is part of the "gear" as well...
I guess the task of the guy is not only to replace the bulb, but to clean and mainly inspect the lantern and it's installation and maybe even the arch structure itself. The bulb replacement is just a "cherry on the cake"...
And because the most expensive part is the presence of that guy there and that would be necessary anyway (for the inspection), replacing the lamp cost nearly nothing...
Plus with a redundant stand-by bulb would be one problem: The optic would require completely separate lantern. And if that would not be powered regularly, the water may collect inside and destroy it that way. So it would have to be operated regularly as well...