yes i could be done easily, not legaly.
a simple toggle switch from radio shack, start at the light and trace the wire, back to its source. this may require disassemble and depending on where you want to put the switch, you would want to cut the wire as close to that as possible.
i would just remove the cars seats and trim then the rug if i was trying to make it as discrete as possible, line every thing up under the rug make small holes for the wires you adding to come out, tape those to the leg of the chair, but while the seat is out i woul look underneath maybe even cut out a section of foam to cover the switch with.,.. ect.