What was useful is the fact SAP offer a really nice tool to handle that. The transaction code is "PFAL" - HR ALE Distribution of HR Master Data. This program relies on the ALE Message Type structure, but is able to send HR data from one systems to another. You could use one of the standard deliver message type, such as the HRMD_A or HRMD_B or even HRMD_ABA (this one is recommended if you use Management Global Employee functionality in HR).
If you dont need all of the infotype provided in the message type, you could create a reduced message type of it and call that. One the functionality, when passing HR data, you could have it go by evaluation path, which allows it to also take relationship on the OM side as well. It will pull the object, create the object, and their related data.
Bare in mind since this require some ALE distribution, you will need to involve the SAP Basis team to help you setup the message type and the RFC connection.
Either case, it beat writting a new ABAP program to extract and load through old fashion flat file.