There would definitely be interest in such items. However the market for such things is so small it wouldn't be a very lucrative thing to do unless you made like a group buy. I'm not sure if fiberglass replacement panels would be the first thing i would pick for my car but definitely a lot easy then trying to rebuild your rusty old parts.
Thanks for your input. i agree not a big market but seeing as there is a language barrier in jp and they seem to add massive value to these frp parts it was worth a punt.