The prime focus of a business analyst is the creation of value.
In the end, value is realized by the customer, therefore taking a customer-centric design approach makes sense.
The first item to be determined is who the customer is. For any engagement, there will be the stakeholders that are realizing the value. Determining those stakeholders and how they get value is a key focus.
The customer is not always the client who is paying for the engagement. Sometimes the client needs to be educated on who the customer is and how they obtain value.
This understanding becomes a key business requirement that is used to measure the success of the engagement.