@BuZz
Ok, so I tried it last night with my existing Pi3 image. It didn't make it past the 1st boot (kernel) screen. I got a number of error messages such as these:

Recovery4.dat not found

Recover.dat not found

startup4.dat not found

Error: 000044

Then there was another message stating that this Pi needs an updated version of the software.

Is there a way to do the update of SD card offline by mounting it?