Yeah, had the same thought and tested it. It is a bit cumbersome, but the idea of it seems to work with linked scenes (though doesn’t seem to update unless the “master” scene file is reloaded every time, so that’s quite annoying).
In a single scene though, I’ve come across an interesting add-on that seems to do precisely what we want, just switching the viewport to activated cameras based on playhead position in VSE: Previz Camera Tools - #18 by tin2tin
Though future developments (at least to accommodate 2.8) seems to have been single-handedly stunted by the unfortunate decision to disable allowing current scene from being added to the VSE.
I think a development of a kind of “master” timeline for the VSE with the features of the add-on would make for an ideal workflow.