Perhaps #11 & #12 would be the pre-upgrade brief and the post-upgrade debrief.

The first gathers key participants and goes over the final master tasks and responsibilities list. Discuss methods of communication to pass the baton and what to do if something goes wrong. The most important thing is that business has an ERP system (the new one would be great, but the old one is better than none) when the system is planned to be used again. Discussing an mitigating that risk management in a pre-brief is essential.

The debrief is also important. It provides lessons learned for the next upgrade and should help to galvanize the team's experience. Key members (to include users that received training) should objectively submit three things that went well and three things that need improvement to the de-brief MC prior to meeting. Once the MC goes through the submissions and determines the juiciest ones the entire group should get together and discuss. The debrief should happen soon after go-live so memories are fresh and accurate. Lastly, adjust your overall upgrade process as necessary for next time using the lessons learned.