Explanation
The following considerations indicate that a new Salesforce org is the better choice for implementing Financial Services Cloud:
The bank wants to use this project as an opportunity to retire customization. A new org will allow the bank to start fresh and avoid carrying over unnecessary or outdated customization that may conflict with Financial Services Cloud features or best practices.
The current implementation is using a product-centric view and the bank wants to move to a customer-centric view. A new org will allow the bank to adopt the Financial Services Cloud data model, which is designed to provide a holistic view of the customer and their relationships, goals, financial accounts, activities, and interactions.
Existing business capabilities and processes can be redesigned to deliver a higher business impact. A new org will allow the bank to leverage the Financial Services Cloud capabilities, such as Action Plans, Relationship Groups, Rollup By Lookup, Service Processes, etc., to optimize their business processes and enhance their customer experience. Verified References: : Salesforce Help Article 6

To ensure the data is loading into the correct fields in Financial Services Cloud, the consultant should utilize a field mapping file with the external system allocation and the corresponding field in Salesforce. A field mapping file is a file that specifies how fields from an external system map to fields in Salesforce. By using a field mapping file, the consultant can ensure that the data from the new custom object is imported into the correct fields in Financial Services Cloud and avoid any data loss or inconsistency.