Doctor Who Theory | The Watcher | Bigeneration time loop

Is Susan from the future?
Is the TARDIS in a time loop?
Is the Watcher actually David Tenant in disguise?!
Who nose...
Note (with SPOILERS):
Something I didn’t fully clarify in the context of the footage, is that the Watcher appears to David Tenant’s 10th Doctor as a “pit stop” of sorts, on his way to meet up with Tom Baker’s 4th Doctor; this is the “through-line” mentioned in the video.