The BA should use the stakeholder engagement approach to help determine the formality of the assessment process to be followed to understand the impacts of the scope change. Stakeholder engagement is a technique that helps the BA identify, analyze, and communicate with the stakeholders who are affected by or have influence on the project. By engaging the stakeholders, the BA can understand their needs, expectations, interests, and concerns regarding the scope change, and tailor the assessment process accordingly. The BA can also use stakeholder engagement to obtain feedback, buy-in, and approval for the scope change, and manage any conflicts or issues that may arise. References:

IIBA BABOK Guide, Section 10.24, Stakeholder Engagement

Stakeholder Engagement: A Key Technique for Business Analysts, BA Times

Stakeholder Engagement in Business Analysis, Business Analyst Learnings