When I saw the first Williams skin with the mirrored Martini logo and found out that the problem couldn't be solved easily I decided to Modify the texture made by McGregor Kereama to look like the censored Martini logo used in former racing games.
Since I'm not a pro-texture creator I've used the first version of McGregor Kereama's skin (Link: http://www.racedepartment.com/downloads/williams-martini-racing.3615/). I hope it's ok for him that I used his skin. If not, I'll remove the mod as soon as he tells me to do so.
I hope you enjoy the skin, if you don't like the mirrored logo.
Williams Racing Alternative Martini Logo 1.0
An alternative skin for the Williams because of the mirrored logo