I used tried out the big johnson EDI model Aards. The creator made head and body seperate and thatfore more Flexes are possible. It is amazing what is possible with that model. You think that might turn out to be the future for daz6 models of yours too? :D
No.
There are far too many complicated with head/body being separated. Most of them to do with the normals. Long story short, there are visible seams that look terrible. It's okay for a robot model, very obvious for an organic model. There are ways around the seams, but they require nontrivial work. They require even more nontrivial work to get them to behave correctly with anything that deforms the mesh around the seam.
All in all, absolutely not worth the headache in my opinion. I don't have any more flexes I want to add to the Daz standard as-is. If anything, I want to remove some that I find to be redundant and unnecessary.