Since the only way to create proper SEO multi-lingual pages is to duplicate pages with an en/ fr/ structure. It would be good to be able to set the lang html attribute per page. So the output would have <html lang="fr" ... etc..
And to help with duplicated pages would be nice to set variables and have conditionals on elements and dynamic items. IF lang = 'fr' show english field, else show french field.
Might be a good MVP while you guys come out with a full solution.