Switching from 4 PSU's to 1 when implementing Cloud Payroll generates errors

Summary: Customer implementing payroll after being live on HCM since 2019 with 4 PSU's. Attempting to change to recommended 1 PSU multiple TRU configuration and encountering error.

Content (required): Customer went live with Core HR and Benefits on Cloud in 2019 with license set to payroll interface. Customer was configured during implementation to have 4 PSU's with no TRU defined . Currently implementing Cloud Payroll with license changed to Payroll. Updated PSU configuration to be 1 PSU with 4 TRU's rolling into 1 PSU. Encountering error on PSU as all employees not in defined PSU organization not having PSU appear on Payroll Relationship.

As updating the assignment to have the correct PSU on the payroll relationship requires extensive changes as Oracle states in MOS document: Fusion Global Payroll: Employee Got Created under Wrong PSUs (Payroll Statutory Units). Script Request to Be Run to Update PSU for Employees for Provided LEs (Legal Entities) (Doc ID 2534541.1); an alternate solution is to leave the 4 PSU's and create one to one TRU's under each PSU. Other options such as using the Mass Legal Employer Change Process has been explored.