I often help to create different language versions of interesting and free WordPress theme by translating myself or correcting found errors in others work. I think that it is strange that nobody asked for one feature: automatic or semi-automatic theme strings translation (not Google Translation button).
How I see that? Let's assume that we have new theme with correct international construction inside (with corresponding .po file and so on). Today I have to use dedicated plugin or .po editor to translate set of strings to different languages. A lot of this strings (often all if theme has simple construction) repeates again and again.
There should be an option in WP inside to create internal database of translated strings which .po editor could use to automatic translate exact strings in another theme and another and another.... With such tool I could focus myself translating other strings (with option to add them to my database to use if needed). I don't need anything like "intelligent" translation or Google Translation. Just simple string replacement when it is present in database. This way my work would be much faster.
Also I can create basic database of most common strings used in WP themes (like "read more", "search", "next post", "previous post" and so on in different languages. Users then could download and install interesting for them themes and apply automatic translation to make it more useful to their readers.
I know plugin like Codestyling Localisation but it also makes me to constantly repeat and repeat set of most common strings used in every WP theme.