PMP Practice: Assess consolidated project plans for dependencies, gaps, and continued business value

River Petersen is managing a government contract to upgrade the air traffic control system across twelve regional airports. The contract specifies detailed acceptance criteria, requires fixed-price milestones tied to regulatory compliance gates, and mandates extensive documentation at each phase for federal auditors. During planning, a team member who previously worked at an agile software company suggests adopting two-week sprints and a product backlog approach to 'increase flexibility and speed up delivery.' The regulatory agency has made clear that any deviation from the approved technical specifications will trigger a full re-certification process adding six months to the timeline. What approach should River take for planning this project?