I don't know that it is common, but it does work very well. You will end up with an amazing result. The problem with varnish alone is that varnish allows water to penetrate to the wood which will cause the bond with the substrate to fail. By coating with epoxy, you create a water tight barrier coat that keeps water out of the substrate. Epoxy will quickly degrade however with exposure to sunlight (UV). Use a good spar varnish with excellent UV inhibitors and it will not only bring the coating to a lusterous, glassy finish, but it will protect the epoxy barrier from degrading in UV. As I thought back on my wood trim, I did remember pulling it all off once during that 20 years for a couple additional coats of varnish - you just need to use caution to not sand through the barrier coat to the wood's surface during prep. I am actually reusing the console hatch door because it was in such good shape and will just be recoating it with varnish.
Cap'n Dan