The modernisation you should not do
Replacement is the default recommendation because it is the easiest to scope and the easiest to sell. It is frequently the wrong one, and the analysis that shows this takes about four weeks.
Fatima Al-Rashid, Managing Director, Consulting ·
Cost-to-serve, by component
The total cost of running a legacy estate is almost never the useful number. Broken down by component, it usually shows that a small minority of the system carries most of the cost and most of the risk.
That breakdown changes the conversation from whether to replace to which parts to replace, which is a smaller, cheaper and far more likely programme.
Compare against doing nothing
Every option appraisal should include no change, costed honestly, including the cost of the risk being carried. Sometimes it wins. When it does not, it establishes the bar the other options have to clear, which is otherwise left implicit.
Sequence for reversibility
Prefer the order that keeps the most options open for the longest. A first phase that can be abandoned at month four without writing off the investment is worth a great deal more than a faster plan that cannot.