Change primary language in online Windows 8.1

Hi all, 

is there a way to change windows 8.1´s primary language via script?

After deploying o standard en-us image at every site of our company, we add site-specific language packs using lpksetup.exe commandline.

On Windows 7, we were able to change default language (which seems to be called primary language in Windows 8.1) using and xml file as described here: http://msdn.microsoft.com/en-ie/goglobal/bb964650%28en-us%29.aspx

With Windows 8.1 this doesn´t seem to work anymore - does anybody know another way of doing it? 

Many thanks in advance, 

Andreas