TL

“1. kephale has a different meaning than usual
2. hypotasso has a different meaning than normal
3. Whenever we have to change the meanings of words to fit our theology, that rings alarm bells for me.”

That would ring bells with me too. And it has when I’ve seen it happen.

For an indepth look at how kephale was used when Paul wrote the epistles see :
http://powerscourt.blogspot.com/2008/01/index-cbmw-grudem-kephale.html

There is a huge amount of research that proves that kephale was not used to mean ‘authority over’ in metaphors. Here is one small quote….

“The foremost example which Grudem uses to prove that kephale means “authority over” is,

“the king of Egypt is called “head” of the nation”

Grudem used this quote on Jan. 19, 2008, on the Gender Blog. However, in Appendix 1A of Recovering Biblical Manhood and Womanhood, he wrote,

19) Philo, Moses 2.30: As the head is the ruling place in the living body, so Ptolemy [Ptolemy Philadelphos] became among kings.
Cervin does not think that head means ruler here because Philo says that Philadelphos is the head of kings, not in the sense of ruling them, but as the preeminent king among the rest. Philadelphos is the top of the kings just as the head is the top of an animal’s body. . . . This example is therefore to be rejected (p. 100).”

Grudem continues in RBMW Appendix 1B to discuss this example. However, he fails to show that it means “authority over.” This is Grudem’s best piece of evidence and proves the opposite of his thesis, which is that kephale means authority. It obviously doesn’t. The rest of Grudem’s examples are similar. However, what is the point of quoting them if Grudem just recycles rejected evidence?”

Again, the continuing problem is that the metaphor as a whole is ignored. It is a ‘head of’ and ‘body of’ metaphor. “Body of” has never been used to denote “follower of”. The word OF makes a difference also. OF is different than OVER. OVER is NOT used.

I suggest that we look at the other uses of metaphors of ‘body of’ and ‘head of’.