6. Clips and Out Takes
This can only be used sparingly and there would be big issues with being the wrong screen size, low resolution and even Black and White shots. On the plus side this has been done before in The Five Doctors to get around Tom Baker not being involved the BBC usage un-broadcast footage from Shada of The Fifth Doctor and Romana punting (picture above). The idea was the Time Scoop failed to capture a particular incarnation leaving them not taking an active part in the episode. The fans might just about bear this if used sparingly but I can't see it being a large part of the solution so I would estimate the chances of this being a major technique at around 15%.