I have a 2014 GMC Sierra and need to get advice to see if what I want is possible. There are a lot of great lighting features on this truck, under bed rail lights, under mirror lights, interior lights, cargo light, etc... What I want is to add a few backup lights and a switch to turn them all on at once. Is this even possible? My main frustration is the rear cargo light has a direct switch, but it will not come on unless the truck is in park. This makes it difficult to check loads while going down the road at night. I think it would be great to get to the lease and while unloading, be able to turn all exterior lights on except for headlights. Any help is appreciated.