I have also been trying to piece together the family of Wesley McGill. I have found that the McGill-Dillard family tree on Ancestry.com is well resourced and has sorted out the wives and children in a way that matches my research. They provide the sources indicating the 3rd and 4th wife, but do not directly list them. They also include a photo of Wesley McGill & Laura Bowman
SEE: http://trees.ancestry.com/tree/14752875/person/157455092?ssrc=

Here is an overview of what I've got so far. I would be happy to send you my gedcom file, which includes my sources. You may email me at: julie_hite@byu.edu. We are related to his 3rd wife.

1st Wife: Laura Bowman, b. 17 may 1848, died 15 Sep 1877. Md 1862. 4 children: George Baldwin (1870-1845), Lillian Elizabeth (1871-1883), Daniel Homer (1873-1907), and Louisa Pauline (Lulu) (1875-1933).

2nd Wife: Dorothy Katherine Bozeman (Dollie), b. 7 Jan 1857, died 19 Sep 1895. Md 12 Jan 1879. 1 child: Emma Augustavia (1879-1951), md. Edmund Dillard.

3rd Wife: Laura J. Wise, b 17 Aug 1854, died 7 Sep 1911. Md. 1 Dec 1896. No children. (This is our line.)

4th Wife: Alberta Stubbs, b. Apr 1884, died 6 Jan 1935. Md after 1911. No children.

If you have additional sources or different information, I'd be happy to share so that we can obtain the most accurate understanding of this family.
Thanks - Julie