The business analyst should use a stakeholder analysis to gather additional perspective, feedback, and detail on the requirements from the NTO team. A stakeholder analysis is a technique to identify and understand the needs, expectations, interests, influence, and power of the stakeholders involved in a project. A stakeholder analysis can help the business analyst communicate effectively with the stakeholders, manage their expectations, address their concerns, involve them in decision making, and obtain their feedback and approval.
A business analysis plan is not a document to gather additional perspective, feedback, and detail on the requirements from the NTO team. A business analysis plan is a document that describes how the business analysis activities will be conducted, such as what techniques, tools, deliverables, roles, and responsibilities will be used. A business analysis plan can help the business analyst plan and manage their work, but it does not help them gather information from the stakeholders. A current state analysis is not a document to gather additional perspective, feedback, and detail on the requirements from the NTO team. A current state analysis is a technique to understand and document how the current situation or process works, what are its strengths and weaknesses, what are the problems or opportunities for improvement, and what are the root causes of the issues. A current state analysis can help the business analyst identify gaps and needs, but it does not help them gather information from the stakeholders. References:
https://trailhead.salesforce.com/en/content/learn/modules/business-analyst_skills-strategies/explore-techniques-i