Yep you can't use GUID's to solve this problem. So my question is do you create the secondary service orders to the parent in sequential order or do you do parallel processing during the create of the secondary?
If you don't do parallel processing of the secondary your only hope to resort the table is you will need look up the creation timestamp of each document and then do an external sort based on that. I did however notice that there is timestamp on the DOC_FLOW segment that is returned by the standard one-order FM's. I haven't examined what this specifically corresponds to, but this might be a more efficient tool to use for sorting based on linkage creation time.
Take care,
Stephen