IIRC they've been talking about the potential of "packaging" up the individuals since they first found them. Packaging being giving them an air tank, face mask, and making them neutrally buoyant them so the experienced divers can push and pull them along the tunnels.
So long as the professional divers have full control over the "package", it shouldn't be a deal breaking issue. Detach the tank, move them through separately, just as the divers themselves do.
It's certainly not safe, as the loss of the recent diver has shown.
Little is known about why he died. I see many people go full tryhard when a child is in danger, doing dumb stuff.
I can see a scenario where he wanted to rush it, potentially cuttin corners, because of doom rainfall scenarios. This makes his death more a psych problem than a dive problem.
Another is age/shape. I used to be a fine skater, did a trick I could do in my sleep at 14 at 30 and fell hard. These kind of coordinations need to be maintained and he was explicitly retired.
This seems like the implementation of that plan?