After some more contemplation (and a few tests with varied success), I think I have come up with the proper game plan:

Before merge starts:
Store original document's 'Saved' state
Duplicate entire original document to a temp 'reference' document (hidden).
Delete Cover page from original document
Convert the textFields to placeholders in original document

After merge completes:
Add cover page from reference document (bookmark) to merged document
Restore text fields in merged document from reference document
Reset contents of original document to contents of reference document
Reset original document's 'Saved' state
Close/delete reference document