I would really like to have some work about people with special permissions on Wikimedia projects (starting with rollbacker, then admins etc.): is retention different than with regular users? if so, how? did some policies have impact on behavior of those users; if so, which? do Wikimedians with special permissions influence development of wiki and how (just in broader sense, of course)? which recommendations could be given based on statistical data? is it possible and how if possible to have real-time analysis of the trends? if possible, a tool would be needed; and so on.
Not a lot of information outside of statistical analysis would be needed, so it wouldn't require extra organizational efforts initially. The initial target would be small wikis and all of them are standardized by stewards. In future it would be good to have such research on all Wikimedia wikis.
So, the only issue is to find a researcher who would be willing to do that. I would mentor such researcher and I would connect him or her with other relevant Wikimedians, if necessary. I don't how how the process related to the finding researcher and mentoring him goes, but I suppose that Dario has clue :)