Vinyl PVC is made soft with volatile plasticizers. Over time especially when exposed to heat and sun they will off gas and can effect surfaces that are in contact. My recommendation (decades in the recreational and industrial fabric trades) is to give it a good long test of a month or more in the summer Sun and see the results. My guess is epoxy will not be harmed. Varnish, which can have its own off gassing, could be problematic. A second consideration is how well does the PVC filter out the Sun’s UV rays.
I am mounting a diamond plate tongue box on the trailer and found some fake diamond plate PVC film that I thought would both add some nice design and protection to the exposed lower front end of the TD. I’ve changed my design motif and abandoned the film idea but it is interesting. If you decide to wrap your TD or just do a few tests please post the results.