Many moons ago, during my undergrad days, I took a Koine Greek course on the exegesis of Revelation from Allan Dwight Callahan, an African American Pentecostal scholar. This is one of the few things I remember from his course. He agreed with the conclusions of your article. If I recall correctly, he interpreted the καὶ as an epexegetical καὶ: “slaves — that is to say, people’s souls.”
Unfortunately, most of what he taught us in that course never got to print, I suspect. I’m glad to see this particular interpretation being published in a peer-reviewed journal somewhere!