I'm setting up an edit for someone that wants to edit some old World War 1 Footage. At the moment the footage has come in with a watermark and no doubt in a few weeks he will be wanting to purchase the footage and replace the watermarker lower res footage with the new.

At the moment I have AMA'd all the material I have into Avid and currently trasncoding it into a lower res editable format (it all came in mp4)

If we were planning to do the edit with the low res watermarked footage, how can I then at a later change what we had to the new hires non watermarked footage?