Looks like the only blocker for Windows 10 is the "minimal unplanned downtime." Although Windows 10 does have mandatory updates, I have yet to see one that requires immediate and sudden reboots. Yes, if you get prompted for an update reboot and delay it a few times, the system will eventually force the update, but a simple workflow change of rebooting the system every night when you're done working with it and are going to bed would eliminate the unexpected updates and the associated downtime.
I'm not particularly concerned about unplanned reboots. The real issue is some Windows 10 updates have caused problems which made the computers unusable until remediated.
There are some points in the business calendar where 1-2 days of downtime is catastrophic. For example, shortly before the deadline for submitting highschool senior photographs to the yearbook publisher.
If we could purchase a version of Windows 10 which allowed her to delay installing updates for 1-2 months until a crunch time is over, that would probably be acceptable.
AFAIK only Windows 10 Enterprise allows that, and I'm not aware of any legal way we can get that.
If we do have to go the Windows 10 route, my contingency plan is to look into setting up a firewall (external to the Windows 10 box) that blocks all relevant Microsoft IP addresses.
