Ship-to and route are not a big issue, you can choose not to redetermine the plant shipping point etc. (Suggestion: you can use one sold-to party for technical purposes and set the same partner functions, shipping conditions and so on as the customer you want to 'repair'. After you finish with the repair, you can block it so that nobody can use it for order entry.)
The confirmed quantities and dates can be a problem unfortunately. I guess you can extract the dates for the confirmed quantities and after you change back the sold-to party you can adjust them as they were. I hope you do not have a very big number of documents. This can be a very tedious task.