Sophia,
great suggestions in this useful summary.
Two observations.
Using the gnso.icann.org web site for our own use makes eminent sense but the key is to get agreement from ICANN senior staff that the GNSO policy and secretariat can update this section of the web site without pre-clearance from ICANN legal. This has been the issue until now. If the issues persists I would suggest with ICANN legal agreement an entirely new URL for our purposes.
There is already a list for Council members only - its called NAMES and is used for updating contact info etc. Its use could be extended for admin matters.