[Cal]

My body is "me" in a sense, but not all senses, and certainly not in the most important senses. My body is not my person, it is not my essence. I can lose parts of my body and not lose who I am essentially. I can exist apart from my body. I will get a new spiritual body.

So while it is not necessarily incorrect to say the Body of Christ is "Christ" in a sense similar to the way our bodies are us, that does not dovetail into the notion that the Father, Son, Spirit and Body are now on some kind of equal footing that declaring them the "four-in-one God" or even "four-in-one" would imply.

Saying "four" when three of the four are the Father, Son and Spirit makes all of the four peers in some sense. My body is not my peer. Neither is Christ's Body Christ's peer.

You wouldn't call Christ and his Body the "two-in-one Christ," so why would you call the Trinity plus the Body the "four-in-one God?"