The following provocative pedigree was located on the web:
http://www.public.asu.edu/~bgertz/family/d0005/g0000026.html#I03700

WILLIAM GRAYSON
    6 Nov 1735 - 17 May 1829
    BIRTH: 6 Nov 1735, SPOTSYLVANIA COUNTY, VIRGINIA
    DEATH: 17 May 1829, ALBEMARLE, VIRGINIA
        Wife: ELIZABETH
        Sons: 1.  JOSEPH GRAYSON 

2.  BENJAMIN GRAYSON
    BIRTH: ca. 1750, ORANGE COUNTY, VIRGINIA
    DEATH: ca. 1790, WILKES COUNTY,  NORTH  CAROLINA
        Father: WILLIAM GRAYSON
        Mother: ELIZABETH

Family of Benjamin Grayson:

    JOSEPH GRAYSON
    JOHN GRAYSON
    WILLIAM GRAYSON
    JESSE GRAYSON
    WREN GRAYSON
    STACEY GRAYSON 

    NANCY GRAYSON
    BENJAMIN GRAYSON

Email from Dr. George Fox: 

As best I can tell, the original origin of this pedigree is a seriously researched article by 

Capt. Edward R. Dittmer on Grayson ancestry in the Wilkes County, NC Heritage book.

He discusses various Va connections and argues that the most likely
connection is to Orange Co where a John Grayson (if I remember correctly) 

of the Ambrose line is known to have two children; Thomas & William. Dittmer 

speculates that there MAY have been a third, a Benjamin. 

He goes on to suggest that alternatively a William Grayson was also present

in Orange County in the 1740's and that he MAY have had a child named Benjamin. 

Dittmer points out evidence that this William died in Orange county. Therefore this 

William is probably not the son of Ambrose that had a very long life (unless there is a 

major error in the standard VA Grayson genealogies).

The reason Dittmer sees Orange County as a possible 

origin for our Benjamin is based on two facts:

1. there are Graysons there
   at about the right time and

2. many of the families in Wilkes came from
   Orange Co., VA.

I have been unable to uncover any evidence for Dittmer's hypothetical pedigree 

but the good news is that there is nothing against it either. It should be noted that 

Dittmer never claimed it to be proven only that it was a reasonable theory.

I one time went over everything our library had on Orange Co., VA and
found nothing particularly useful. I have also asked several people on
internet who are peddling variations of Dittmer's theory what the evidence is-
never having received a meaningful response.

Since I believe the Stacy Ellzey BG theory you originally raised is
now probably refuted (see our write up) & since Ambrose's BG is not
credible (born too early plus other issues) I would concur that
Dittmer's proposal is the current best guess but it remains 100%
unproved.

With respect to the specific proposal you sent along, the following
needs to be appreciated:

(1) I am not aware of any evidence for a Benjamin Grayson in Orange
County. In fact to the Grayson research community has carefully
examined every known Benjamin found in Virginia between 1700 and 1790 and 1700's 

shown that none of them are the BG that went to Wilkes. To my knowledge there 

are currently no remaining Va Benjamins to study.

2) Even if there is a recently discovered Benjamin in Orange Co. we
would also need evidence that he is the same one as in Wilkes.

(3) The children of WILLIAM GRAYSON (1735 -1829) have been 

described by well known researcher Cynthia Snider in her Grayson book 

and do not include a Benjamin.