Not sure if this is the place for this but I had an idea for an exercise where your given a simple question in the language that you are learning and you answer in kind, it could help to see if your comprehending the language
Open-ended questions would be very difficult, if not impossible, to program.
Duolingo has a test feature called "Stories" that is currently only available for English speaking students of Spanish and Portuguese. It lets you read and listen to a story and periodically answer questions about the story. The questions are in a variety of formats. It's pretty fun. I would love it if they'd release it for French!
Yes and no questions, where you have to echo the question might work, but I agree that the stories offer the best incarnation of this idea (roll on other languages...LOL)
It's not a bad idea to be honest. But it might be tuff for the moderators to write all the answers that are possible, no ?