"do not go around rolling out patches and upgrades like this on primary production systems"
I've worked development on several large bespoke systems. Some had complete development and test environments, some did development testing on the live system.
The latter were substantially more stressful to work on.
So some people do.
But if you're at the design stage it's much better to set up a way to switch the whole system to a "test" company and make all (well IRL as many as possible) of your mistakes in that system.
Biting the hand that feeds IT
