I hear you on the eggcrate thing. Maybe some kind of wood fascia that can sit around the tank, still be open top, but basically look like a canopy .. then jumpers would likely fall back in.
I agree with your reasoning however, fairy wrasses are terribly prone to jumping. I would not feel comfortable with some in an open top tank.
You know, Banggai's are often cited for being not very colourful, but .. you know what, they really have a sort of endearing quality once you have one or two. I can't quite put my finger on it ... they're pretty, and you get to know their personalities. The two that I've had over the years, have been really nice fish. The only thing is, I lost both of them to the same thing .. it's weird, not sure what or why, but they would be fine in the morning, and then in the evening I'd find them on their side in the sand, bloated. Some kind of intestinal malady? Just weird to me that both fish would die such similar deaths, years apart. One thing that they had in common was that they were exclusive mysis feeders, so I wondered if I had fed them a bad mysis or something.
Anyhow other than that though, they were neat fish. I do recommend them if you can find them, maybe hold out for captive bred though, since their wild numbers are in trouble.
