Often when I have seen someone develop the repeatable "perfect environment", be it as a set of scripts or a machine image or base VM etc., the mistake is to think that the job is done.

The hardest job is to keep going and create other "perfect environment"s moving forward to cover different versions of OS, servers and apps. This then shows that the difficulty is that there is likely to be a reasonably large number of variants. That really complicates matters.