This zipped copy of the 1985.SQC file, which me squad mate, Veit Wiessner, forwarded to me, was taken from someone who has already completed the campaign. Using it, you can revert back to any campaign mission you want to. Of course, the file reflects someone else's campaign scores but, considering that OFP doesn't offer a historical display of your prior campaign accomplishments, who cares?
Your existing 1985.SQC file can be found on your PC in the following location:
\OperationFlashpoint\Users\your_player_name\Saved\Tmp
Before replacing your old copy with the new one, make a backup copy of your old 1985.SQC file. Then simply unzip the downloaded file and replace as a new copy of the 1985.SQC file.
When you go back into the OFP Campaign Book, you will now see an almost complete list of all the campaign missions available. You can now play any of them at will. However, by doing so you will spoil for yourself the campaign story and sequence. My personal suggestion to everyone is to select the mission after the last one you successfully played and click on REVERT. This will return you back to where you last left off in the campaign and require you to successfully complete each mission in order to advance in the campaign.