I found the article very interesting. As the sole DBA I am currently supporting 2 clustered environments in 2 domains. The headache I am going to be facing next summer is the replacement of the 2 servers in one of the clusters. When we replace hardware, we also upgrade OS. We do not upgrade the OS on existing hardware. The reasons for this can be the subject of another post. This particular cluster is running Windows server 2008 R2 Enterprise. When we replace the hardware these servers will move up to Windows Server 2012 R2. Can Win 2008R2 and Win 2012R2 be clustered together?
If you have the two boxes sitting there you might consider these steps instead.
1) Build the second cluster.
2) Install SQL and restore master. (upgrade SQL if needed).
3) Restore MSDB, Model, and set up anything else you need.
4) Mirror over to the new cluster.
5) Make sure everything that needs to reach the new cluster can, make sure all the packages, web servers, app servers, anything can reach and talk to the database.
6) Double check #5 about 3 more times. Have someone else test it.
7) Fail the mirror over safely to the new cluster. After it's run there a few hours/days/week.... break the mirroring and shut down the old cluster.
8) Find something cold and put your feet up for a bit.
This is a personal approach as long as you have the hardware / licensing / time to support it. There may be other ways, even better ways.