Hmm… can you get more cut-away (B-roll)? Perhaps from a stock footage library? You could use the same cut-away twice as long as there is sufficient time between them. Maybe add a Black & White effect the second time you use it to give it a different look?
On the background, I would use the same background for each. This should give you better continuity. If you wanted it to look like the interviews were done in several locations then maybe have 2 or 3 different backgrounds. Having 7 sounds like a lot to me. You could always do a quick fade up from black for the changes that have no cutaway. Quickly added a lower third with their name is also an indicator that this is a new person.
Sometimes making the change obvious like doing a push left or right is a good way to show you are changing people. If you are cutting back and forth between the same two people then by all means change their background and position in the frame. Since this is all chroma key have one on the left and the other on the right. The change in angle should help with the cut. Of course if their bodies are angled facing the center of the frame, moving one of them to the opposite side will look unnatural because they will be facing off screen. It’s hard to say without seeing the footage.
I don’t know who shot this but hopefully the next time you can have whoever is shooting, do so with the edit in mind. I’m always running the edits in my head while I shoot. But that’s the advantage of editing your own footage. Getting lots of B-roll is always very important.
~jr
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