I am not sure you are addressing your question to me but I can assure you that I am not saying anything about the spelling of the surname of the Susannah Baynes in question or of any other Susannah Baynes. As to the points you raise in your message I would offer the following:
I attempted to show in my Carter Wives - Susannah Baynes piece that the Thomas Carter who witnessed the 26 Sep 1730 deed in Henrico along with Susannah Baynes was probably the Thomas Carter of Turkey Island rather than either Thomas Carter of Goochland or his son Thomas, Jr. The connection you note was, I believe, first made in the Malone book on Josiah Carter.
Thomas Carter, Jr. of Fleming Park Creek did indeed name two of his children Baynes and Susannah. I would not however assume he named them for the Susannah Baynes on the 1730 deed as I stated in my piece. As I point out the Susannah Baynes who witnessed the 1730 deed did so with a signature while the Susannah Carter, wife of Thomas Carter of Goochland, signed the 1735 deed with her mark.This suggests to me that they are two different women with the same given name of Susannah.
That the name Baynes evolved over time to be written Banes can hardly be surprising in light of the Bays discussion you begin with.