I've managed to have a quick look at this now.
When requesting fonts from Google, you can list the subsets that you want. These subsets provide the glyphs for various languages. The "latin" subset provides (usually) all the glyphs for English, French, Spanish and German.
"latin" is also the default when no specific subsets are requested, and the Woo framework does not ask for any specific subsets.
Now, there are over half a dozen subsets, and you can request any combination of these, including latin-extended, greek, cyrillic etc. The more you select, the bigger the font files will be. However, not all fonts contain all the glyphs for all the subsets - that is a bit of pot-luck at the moment, but is not the issue here.
So, the Woo framework puts the code into the header of the page to request the Google font. That cannot be extended to support the subsets - it is just not written to be extended. It can possibly be over-ridden, so this plugin can replace the header font requests, but I would rather not get into that, in case a Woo Framework update is then broken by doing this (I just don't know where Woo is taking this next).
Something for me to explore is perhaps loading the non-latin subsets separately. The Woo framework can load the latin, and the plugin could then load the selected non-latin subsets on top of this. Whether this will work or not, I really don't know. I'll do some experimenting and see if it is a possible way forward.