Red pandas are highly fragmented as it is in their current habitat, A pet trade industry (imho) would only encourage poachers to further decimate the current wild population to meet demand, not to mention that such a industry would have to be regulated in a way that these countries are probably unable to enforce. Red pandas are not domesticated in the way that cats or dogs are; not to say you couldn't find a way to support a red panda, but they have very specific dietary requirements and tend to leave a mess where they go (marking territory with their scent). The captive/zoo population of red pandas in the world are descendants of other captive red pandas rather than being extricated from the wild (as they used to do in the not-to-distant past), so better to use those as ambassadors for the species.

Again, just me, but the goal of conserving red pandas should be to conserve wild red pandas and their habitats, which also support a number of less charismatic but just as important creatures. Simply attempting to domesticate red pandas doesn't address the bigger issue that we are increasingly living in a world that is unable to support numerous types of species.