This is an extremely ambitious program. On the other hand, much of this work was done as part of the Comprehensive Assessment of Water Management in Agriculture (see D. Molden, ed. 2007). I think you can build on this, and also ask the question, what has changed since that study?
I would suggest you place special emphasis on innovation: what are the possible new ideas for acheiving global food and water security? This would include assessing ideas emerging from scientific research as well as from local on-the-ground experiments (whether managed by communities, individuals, NGOs, CBOs, or governments).
Finally, I think equity should be a major theme of the work and report. We pay lips service to gender, youth, marginalized groups etc in all documents but we do not think seriously and deeply about what we need to do to overcome these kinds of inequities. Such a focus --serious and critical -- could lead to new ideas that could be game-changes. If you do not do this, I fear this will be just another report discussed at various forums and then shelved.
Doug Merrey