Geni, there is one basic misconception in all your arguments. You are speaking about reduplication of effort and about efficiency. But it is not the goal of the foundation to cram the minds of all the world's population with as much information and knowledge as possible. We don't want to rear brain machines. Wikimedia has no social agenda to change society. Being dumb is okay. It's okay if you don't know the basic facts of history. It's okay if you don't know the differences between McCain and Obama, between Merkel and Steinmeier or between dos Santos and Samakuva. It's okay if you don't know any foreign languages or even your native language poorly. It doesn't matter. We don't want to force people to learn. But if people decide, they want to learn something, Wikimedia is there to help them. That's our goal. To provide the possibility.
Your philosophy matches the Borg philosophy. Assimilate as much species as possible to become as efficient as possible. Do you remember that in Star Trek every species has one characteristic feature or topic? The shortest possible description of the Borg is "Hive", of the Klingons "War", of the Ferengi "Commerce", of the Vulcans "Reasoning". The topic of the Humans is "Humanity". You are a Borg, not a Human.
Personally, I would rather die, than to live in a world speaking one language, subject to one legislature, all people watching the same movies and reading the same books. Diversity and imperfection is what makes life interesting. It was you, who said "Totally bi-lingal situations are not long term stable". That's true. Therefore don't enforce global bilinguality. It would inescapably end in a monocultural world.
When I was a child, I loved our holidays in Denmark. It was exciting. Foreign language, foreign mentality of the people, foreign food etc. The differences made it interesting. Today some things have changed since my childhood days. Many typical discounters of Denmark where replaced by international discounters, for example Aldi (for the US guys: Aldi is the German equivalent of Wal-Mart [Aldi is present in the US too, but not as well known as Wal-Mart, I guess]). You can buy typical German food in Denmark and typical Danish food in German discounters (well, most "typical" Danish food is going to be unknown even in Denmark itself, only "stereotypical" Danish food is sold elsewhere). Wherever you go, there are Burger Kings and McDonalds (in almost every single country in the world). Diversity is the salt in the soup of life. But globalization (and a "common language" is part of globalization) makes the soup very insipid.
Marcus Buck