another thing that might be useful is to make the site support multi language theme -
e.g.
if the theme name is "default", and the language is "spanish" make it try to load the theme from default_spanish folder (most specific) if folder does not exists - try the regular "default" folder.
This is important because sometimes different languages need a whole different layout - words in English, Spanish Arabic and German are not the same lenght.
We have made this change in our code, and it works great.