Thanks for the suggestions so far!
I think the most time-consuming part will be having the existing footage slide over to make room for the incoming panels, all while staying centered on the subject (like the NWU video did with the four videos at 00:33). That’s what I was hoping a third-party (or other) solution might offer (which is different from the Tokyo Split plug-in, since that slides on media without displacing the underlying layer) — essentially a way to define a center/anchor point, and have that remain visible while the layers slide around. My primary timeline is similar to the example video, with interview subjects shot against a white background; I’ll want to make sure their faces remain visible as the B-Roll media slides in from the sides. Do you know of a better way to do this?
Another potential challenge I see is changing the animation if the client requests a change to the primary interview timeline later in the process (i.e. swapping out one soundbyte for another); if the animation was more automated I could potentially replace the target clip, but if I’m doing it by hand I’ll need to redo the animation manually. Any ideas?
P.S. I am unfortunately currently unfamiliar with Motion; I do my animation work in After Effects. While I’d love to learn more about it at a later time (especially since it integrates so well with FCP X), I’m afraid there isn’t time learn enough to create custom presets for this project. Thanks for the suggestion though, Robin!