Regards SEO – looks like plugin will not create another page that would be useful for SEO? – yes, only native language have page, another language text loads by ajax (Ex: http://pluginus.net/mea/mealingua/1) lookin for variable in link. I thought about this, but now no idea how to make that to live simple. Maybe do such: each translations created new post and them is as descendants of base post which is in native language. But this is another architecture… but it is possible I think… maybe do such on free time =) (about 1 week period)
Do you have list of languages available? – in settings you can add so many languages as you want
What is used as base for languages – Google translate or similar? – no service using. Google translate is good to translate for for themselves, but seriously it is bad idea. Better to translate by hands and people will read it with more pleasure =)
What about first point: I think will do that. Now its have links on flags, but for robots it is the same post….
If any questions write here, and I will think how to decide a task:)