Some good points. Some more context: this made a manual process semi manual. You still had to enter the data and the target programs still flew around (on screen) on the background. I think the risk profile was similar.

> Unit tests, integ tests.... was there a preprod environment for it? A trial run? Can you safely roll back if / when bad data shows up?

Nothing of the sort :)

But... Let the adequate be the enemy of the less awful?