[crtlaltdel]

solidwood faceplates are not uncommon. take a stroll down the electrical section of a major chain hardware store and you should be able to find a few. a lot of them seem to be made of bamboo. as for the dielectric properties, even in a “humid environment” its unlikely to be an issue. i mean, does a foggy morning short every outlet without a protective cover? if your voltages were high enough, sure you could draw an arc through the humid air...but it seems like you would have to hit closer to the kV range