@wardmundy -Ok, finally came back to test these after hacking them out the other day. Spent some time trying to break them tonight. After a little cleanup I think they are OK.
These are probably overkill, but I couldn't bring myself to post these without at least basic checks to prevent trashing the system.
- randomizepi - changes PTUUIDs and UUIDs on the current root and boot partitions.
- resizepi - resizes current root partition to fill drive. root partition can be resized online while mounted. Optionally takes a percentage to expand to. Optionally can be passed another unmounted partition to expand.
An additional note - I meant to go back and add a no-reboot flag to the randomizepi script. The original "find root partition" method borrowed from a raspbian script broke after changing the IDs and the script could only be run once, so I felt a reboot was warranted.
The final "find root" method seems solid before and after changes. I ran multiple times without reboot in succession, before, after and intermingled with multiple runs of resize script expanding to 50%-55%-60%-etc.
Tested on your image, Jessie-Lite, 3b+ hacked Jessie-Lite and Stretch-Lite.