After being reminded of phabricator:T130470, I think we should make sure any document of this nature includes guidance about documenting lessons learned from failed projects and deployments. To not summarize and document past failings (and successes!) is to waste both donor time and money in an unacceptable way, in my opinion.
As noted in a separate thread, I haven't read everything written here, so this may already be covered in this guideline.