Administrators are able to use the "login as" feature via the User Interface. However, this isn't possible via the API. Please add this feature to the API.
This will improve the user experience of background automations. For example, I recently implemented a Proofing automation that marks tasks complete in WF when certain Proofing stages are approved. This replaces the need for a user to manually go onto the task an mark it complete. However, the notification sent to the team indicates that the task was marked complete by the "Automation User" not the user who approved the stage. This causes confusion. If the "login as" feature were enabled in the API, the automation could mark the task Complete by the actual user proofing user. This is one of many use cases.
When adding this feature, it's important that WF include the "on behalf of" message in the audit log, just like it does in the UI version of this feature.