I don't think women should wear kilts unless they 'have' to, like in a uniform or for historical purposes. (If a Polish guy can play a Scottish soldier in a reeanactment, why is a woman wrong?)
As someone who has been a reenactor (mostly American Civil War, Spanish-American War and other assorted periods), I have no problem with women in the ranks, as long as their is a lot of documentation for their presence. If there was a woman that served in a particular regiment disguised as a man, and it can be documented, then fine. Otherwise, it's an inaccurate portrayal of history.

As far as Scottish regiments go, I'm not sure if there were any women who ever served disguised as a man (Sav, any thoughts?), but it is correct to have other nationalities in the ranks. Many "Highlanders" were actually Glaswegians and other Lowlanders, English, Irish, and one story comes to mind from Mr. Kipling's Army by Bryon Farwell of a Gordon Highlander seen praying in a synagogue in Aberdeen!

Even today, there are a number of "Scottish" soldiers from Fiji, other Commonwealth nations and last but not least Nepal, as a detachment of Gurkhas were seconded to the Royal Scots.

Pipe Bands are a different story...

Regards,

Todd