Thanks Colin and Marcus for your comments and advice, it's very valuable have the viewpoint from people with experience in developing these kind of projects before and that knows all the pit falls and challenges.
Yes, the idea is to develop the core functionality first and later add extra plugins that would enhance the learning experience. And the core functionality as I see it is to create one activity that is purely based on peer-to-peer reviewing. From your comments I get a bit mixed messages. If many Moodle courses are MOOCs, then how are they solving this? Are they using only quiz-time activities? Because otherwise our ambition is different from other courses, since we want to use peer-to-peer reviewing and also that the activities are very open and encourage creativity. It's true that we're giving away learning to the learners, that's the point. Of course I see challenges with this approach and it entails a lot of uncertainty, therefore it would be great to hear from a project that has used a similar approach. I also agree with you that the trialing is essential. BUt, as soon as we have tested one activity successfully we can replicate that with all (or most) our other activities, since they all follow the same logic.
I would like to inquire more about your concerns that we easily could be monstered by this project. It is of course vital for us to be conscious about these risks. You say that Moodle is a good place to start, meaning that it could be that we move over to other tools if necessary? Personally I would rather make sure that our core ideas are manageable within Moodle and then stick to Moodle. We don't have time to change platform later in the project. Or do you have something else in mind when you talk about tools?
And about documentation, of course we have all our learning material documented outside Moodle.
And about designing the tasks for the learners with the right level of difficulty, our challenges are designed to suit students with different levels of knowledge. Since the challenges are open, experiential and creative, the students will naturally find their level. Of course this approach as it's challenges, but right now it seems feasible to me and that any problems will reveal themselves in the testing phase.