You could simply add the following macro to the mailmerge main document that's supposed to output the second version:
Code:
Sub MailMergeToDoc()
Application.ScreenUpdating = False
Dim Tbl As Table
ActiveDocument.MailMerge.Execute
For Each Tbl In ActiveDocument.Tables
With Tbl
.Columns(2).Select
Selection.Copy
.Columns(1).Select
Selection.Paste
.Columns(3).Delete
End With
Next
Application.ScreenUpdating = True
End Sub
Clicking on the 'Edit Individual Documents' button will intercept the merge, finishing it and re-arranging the output.