While I am not as active anymore I have contributed to Picard in the past (and still do if time allows it), so I might say a few things here.
I don't think there has been any thoughts on the development model for Picard, nor is there any strict model followed. In the early days it was mostly a single developer, supported by patches from the community. In the last years a lot of people have contributed and there is a small set of people who are more active. If anything it can probably best described with the loose definition of the Bazaar Model. But basically people just provide patches on Github for issues they find most important.
To be honest I think Picard currently lacks developers who contribute regularly and have a clear roadmap. And maybe it was not the best choice of software for your university project So if you feel like it just submit some patches and start to help on the development side.
Maybe some of the more active developers, e.g. @Zas , @Bitmap or @Mineo, can say more about it.