Unwarranted concern that I'd have to make system changes that would need to be committed to disk and rebooted (e.g. network configurations across twin NICs, including static configuration for the Mesa-based LAN interface (separate to the main interface) - usually if you have to tweak system files you're either restarting services or rebooting. My expectation was that the install was booting from a read-only filesystem into ram - I think that's what the Debian install does (can't remember now), BUT... just tried a boot from USB and was able to copy my machine config over, rebuild my custom HAL components, uplift my machine configuration automatically) and got the lathe running under Mint/LinuxCNC 2.8 within about 10 minutes.
Too late to cancel the same-day order for the removable drive-bay adapter.
Mint looks, for the 15 minutes I've played with it, much more comfortable than Debian.