.....I didn't really think about that. What about applications ported with winelib, can you use pthreads with them? If such a wrapper was developed to run Mozilla_W32/Wine could you then use winelib to port the application and use linux_mozzila/gecko?
I don't know what Winelib supports, have never played with them. In any case, no matter which approach you take it will be tricky and time consuming. I have a feeling going linux mozilla native would be more painful, but I can't back that up with actual investigation. Just a hunch.
-James