I'd be happier to see the fuse directly from the "master" (CB?)
reasoning....protects switch and wiring to the light. If other items are on the "master", provided the addition is fused at the correct value, a fault will isolate it, whilst not compromising anything else on the same "master"
I would guess that your" Earth" would need to run back to a central point. using the airframe as a return, could possibly exacerbate electrolytic corrosion. that's not a good idea.
I am not an Avionics Technician, or Electrician, therefore the above is possibly worth what you paid for it.