I really don't see the reason of going through all the trouble of dying a wig with a sharpie if you are just going to get a color that already exists.
Anyway I can think of two ways to make it. The first requires less cutting and styling abilities and the second is more advanced.
Try finding a wig similar to his hair without the ponytail (this one on amphigory looks like you will have enough fibers to style into a more wavy/chunky look) http://amphigory.com/wigs_l_spikey.html
as a base to work with and then make the ponytail with a package of fibers http://amphigory.com/hair_kanekalon_silky_braid.html
and some got2b freeze spray to get it into the shape you want (after you spray on the got2b hair spray have a blowdrier go over it, it WILL stay in place lol)
I think if you attach the fibers onto the ponytail holder well (make sure the fabric is stiff enough to stay up like that) you can just sew it by hand onto the top of the wig and there shouldn't be any issue =)
Unless you get a thicker wig like a femme fatale http://amphigory.com/wigs_femme_fatale.html
I can't see a longer wig being able to be cut so short without needing a large array of wefts. While this way you wouldn't have to add the ponytail in with wefts I think its a total waste of the wig to cut it all off lol, also while I've seen it styled in a large number of ways I've never seen it cut so short, so this might not be the best option.