Isolating video of a specific resolution

First, some background/context for you. It is common when working on large projects to bring the video into the system at a low resolution (to save drive space and/or to make it easier on the computer to play the media). Then, once the creative process is completed, the low resolution media is deleted and only the portions of media used by the sequence are recaptured at a higher resolution (for example, 1:1) and all the effects are re-rendered at the higher resolution as well.

Just as common, is bringing in some video at low resolution and some video at the finishing resolution. For example, I might capture 100 hours of documentary footage at low resolution (20:1), but import all my graphic elements (stills and animations) at 1:1. This way, when I reach the finishing stage of the project, all the graphic elements are already at high resolution and set to go. In this instance, I would only want to delete the video at the low resolution (20:1) to clear...