Reinstall if upgrade fails

[wkk2]

I have system at a remote location running 2.0.3-Release(amd64).  It's a Dell PowerEdge R320 with a 4 port Intel Pro/1000VT, and two mirrored SSDs on the embedded SATA.

I would like to upgrade it to 2.1.2.  Unfortunately, months ago I tried a 2.1 beta and encountered problems.  The memory stick booted but on disk reboot there were issues.  So I stuck with the older release.

Now I need to upgrade and I'm worried about recovery if it fails to boot 2.1.2.

What is the best way to make a memory stick that will restore 2.0.3 with its configuration?  I need something as simple as shipping a ready to go memory stick so a non-tech person can accomplish recovery.

It looks like I can copy a saved configuration to the memory stick  conf.default/config.xml but I'm not sure about what the install will do regarding the mirrors disks.

Hopefully, the system can just do an update but I need a fallback strategy that doesn't involve an airplane ride.