I like the idea, but I think you should keep the same set of questions for everybody. The only one that seems to be personalised is question 4. The rest could be answered by everyone. If people know what questions are in advance you will probably get more interest as people know what to expect and whether they'd be OK answering them. It will also be interesting to see everybody's answers to the same questions. Maybe people could propose another one or two questions that can be asked.
Having the same set of questions is good and I agree with you that the participants in the interview should answer personalized questions directed to them since not all members here are posting in the same board or doing the same thing on what they are doing in the forum. This allows you to see their perspective on their role in the forum. Having personalized questions for DT members, or Merit Sources, and people active in their local board should also be considered as they definitely have other questions to answer set on their perspective.