However, there is an obvious need for a common language when playing team games.
Agreed. What is not
obvious to me is why you blindly assume this common language has to be English...
My counter-proposal is a little more involved, but it seems a lot more "non-Anglocentric" and, in general, a much more thorough solution. However, it suffers from one massive issue (which, I think, is pretty much inherent to this problem), see the last paragraph, even if you want to TL;DR the suggestion itself.
On the user profile, include an explanation like "Many WL games involve team play, coordination with other players and in general, communication with other players. Please select the languages which you speak well enough for these purposes."
(Displaying that text in English, as well as displaying the (crowd-sourced?) translation, if available, for the country that person is playing from and/or the country-specific extension on their email address, would mean only a very tiny number of people would not be able to understand what's being asked.)
Then include a list of languages, depicted by flags to prevent another can of worms, with checkboxes. (Don't use dropdowns, that's just asking for somebody to speak more languages than you've taken into account, as well as inviting people to rank all the languages they barely speak a few words of.)
Start with ten or twenty common languages and have an "other" field at the bottom, so people can enter requests for more languages. Add based on "enough popularity". Keep in mind there is no one-to-one mapping between languages and countries, so use that god-awful abomination of the US/UK-mixup flag if you insist, but whatever you do, don't have them as separate choices. Same with Standard Dutch and Flemish Dutch: anybody who speaks one of them will be able to communicate with somebody speaking the other, so just group them up. I personally have no idea whether Standard Portuguese and Brazilian Portuguese should be separate (same issue with the various "flavours" of Spanish in Europe and Central/South America), but I bet the people who speak those languages can tell you.
On every game, have a dropdown for "chat language" (combined with a "Default language for newly created games" setting on our profiles). I'm not fully sure, but I'm inclined towards allowing this to be left open; I for one don't mind messing about with Google Translate. Then again, I nigh-exclusively play multiday games; I can imagine language problems being a more pressing issue in realtime games...
Then we're left with one crucial design decision: what to do with games where the set language doesn't match any of the languages the player claims to speak...? Hiding them altogether seems overly aggressive (and, will probably result in a lot of players just selecting all possible languages, including the ones they've never even heard of). Displaying a warning "The game creator has asked for chat to be in a language you don't speak, are you sure
you want to join this game?" is too easy to ignore. Both approaches run the risk of rendering the entire system rather pointless... (Including an actual test
, where people have to proof
a sufficient command of a language seems completely unrealistic; if you want to suggest doing this, please explain how you envision it.)