Well this has recently happened for the last time.
I will never understand why anyone would consider having 5 unwanted balancers and balancing itself all enabled by default anything other than a really stupid idea.
Even less how physically disconnecting 16 hard drives OR stopping balancing on five pools whilst "being quick about it" is a viable work around. With one pool there's a very slim chance of catching it on time. With five there is zero chance.
So it would seem that for the last 7 or 8 years I have been "backing the wrong horse."
Drive Bender "Cascade Mode" is everything I have ever looked for in DrivePool. added to that Drive Bender strangely/sensibly also has a default start-up strategy of doing absolutely nothing until explicitly set. A real shame it's never caught on here.
Anyway over the years I have had my moneys worth, but it's time to call it a day.