Why not transform Duolingo into a tool not just for learning another language but also for improving your command of the language that you already know while you learn another language?
Wouldn't this give people even more incentive to learn another language and do translations — that in doing so, they would improve the language they already know?
Translation exercises already help you improve both languages, but perhaps you could also work with, for example, Spanish and (advanced) English skill trees simultaneously?
Each lesson and each translation could have an impact on your progress in both skill trees.
Hey amichail, that sure is a pretty good idea - and pretty close to what I'm actually doing: As a German native speaker I use Duolingo to learn Spanish, but to do so, I have to use my English skills... :o) Well, as I said, I totally second your idea of two skill trees - one for the new language and one for your native language!
I also agree with the premise of the question (presumably like many others here, I did not start learning the language with Duolingo) and have a related suggestion: If I learn Spanish as an English speaker, I would also like to be able to translate the other way around (from English to Spanish). I know this is already possible as a Spanish speaker learning English. However, this does not lead to idiomatic translations (which is the whole point of Duolingo). Therefore, my suggestion is that there should be a way for English speakers to translate (in this case) from English to Spanish and for Spanish speaking English learners to get points for correcting this (attempted) translation before it gets used as an actual translation. Depending on how many mistakes there are, the translator could then also get points for this. Any thoughts?