Anything that fails isn't moving anything anywhere. And in the type of place that has a dysfunctional, legacy software system running core business operations,

Anything that fails isn't moving anything anywhere. And in the type of place that has a dysfunctional, legacy software system running core business operations, don't count on all the other ducks being in a row (anything resembling agile, ability to release to prod on a reasonable cadence, ability to provision sufficient test data, working test systems, etc). If it's an internal system that you've been working on and maintaining... for 10 years... maybe (just maybe). If you're a consultant stepping in, I wouldn't touch that option for love or money.