For record access control integration with an external system, what option should the Architect consider?

The correct choice focuses on maintaining related SObject_share records through the SOAP API, which allows for the manipulation of sharing settings directly associated with specific records. This is crucial when integrating Salesforce with external systems, as it ensures that the access controls are consistently applied and manageable from both the Salesforce platform and the external environment.

Using the SOAP API for this purpose is beneficial because it provides robust functionality for updating the sharing settings of records, including creating or modifying share records. By controlling access at the record level, the integration can ensure that external systems have the right visibility into Salesforce data without compromising the security model.

While other options touch on important aspects of Salesforce data management and security, they do not directly address the integration need concerning record access control. For example, altering the role hierarchy or creating new sharing rules may involve broader changes in access management but would not specifically allow for granular record-level access adjustments as the SObject_share records do. This makes the selected answer the most appropriate option for effectively managing record access in an integrated environment.