I've thought exactly the same and I think now might exactly be the right time to bring it back. However can the client tell to the server if it consents or not?

I've thought exactly the same and I think now might exactly be the right time to bring it back. However can the client tell to the server if it consents or not? Second problem is of course that malicious or lazy site admins won't use P3P just that they can annoy users to click Accept.