Thanks for getting in touch. It is indeed still on my TODO list to get back in touch, apologies for not doing sooner. This is still something we're very interested in (me in particular).
I (and others in the project) are available at firstname.lastname@example.org. In a nutshell:
* We have two projects I can think of that would benefit.
* Firstly we are in the process of porting the website to a new design (and one which is easier for contributors to submit changes to).
* Secondly we are conducting a complete overhaul of the F-Droid UX (complete with several of our own funded user studies from a UX designer).
Both of these need some more work before I'd be comfortable suggesting them to students. The last thing I want is to suggest a project for them that will be outdated and changed by the time they have completed any analysis and provided suggestions. However over the coming months they will stabalize and it is at that time that it would be great to organise something like what you described.
Although we are conducting user studies of the F-Droid client UX, after all of that is done it would still be worthwhile going into the future to periodically study the usability. For example, different cultures among users, perhaps design trends change, perhaps we receive new contributions that update the UI, etc.
I look forward to continuing these discussions.