An SAP programme is rarely delayed by the software. It is delayed by decisions that were postponed because nobody owned them. Answering a small number of questions honestly, before mobilisation, changes the shape of the whole programme.
First: what problem is this programme solving in business terms? If the answer is a system name rather than an outcome, scope will grow with every workshop. Write the outcome down and use it to settle later arguments.
Second: who owns each core process? Not the project role, the permanent owner. Design decisions need a person who can say yes and live with the result afterwards.
Third: how good is the data you intend to migrate? Master data quality determines how long the go-live weekend takes and how much the first month-end hurts. Test extracts early, not during cutover rehearsal.
Fourth: what will the business stop doing to free up its best people? Programmes staffed only with available people, rather than knowledgeable people, produce designs nobody trusts.
Fifth: how will the solution be supported on day 31? Hypercare ends. If there is no operating model behind it, the workarounds return quickly and the benefit case quietly disappears.
None of these questions are technical, and all of them are cheaper to answer now than in month nine.