I know it's an old topic but I would like to explain my experience in my last two trips.
Nowadays I am travelling with the diving equipment (drysuit incluided if needed) and the camera rig in this way. For the diving equipment I am using a normal lightweight samsonite suitcase, I adjust the weight between 20-23 kg depending the air companies. And for the camera rig....The housing, big macro port, with the camera, and the lens inside, with 2 clapms and an arm as a handle, and an attached strap hanging from my shoulder like a bag. This way passing the airport filter it's pretty smooth. The rest of the rig goes into a cabin suitcase with me during all the time. There is place for the two strobes, arms, clamps, chargers, batteries, dome port, lenses, laptop.
Only in the Madrid airport I had some issues with the cabin suitcase and I had to empty all the elctronics and pass the scanner with 4 different trays.
And I had another issue with the weight of the cabin suitcase (16kg) in the Tenerife north airport, I usually hide that suitcase when I go to the airport check- in, just because I don´t want them to weight it, but this time I was distracted talking with a friend. The flight was to El Hierro with a small turbo propeller plane and they only admit a 6 kg cabin suitcase. So they offer me to put for free some of the stuff in the cabin suitcase to the big suitcase, I did it, suffering for my laptop, and the strobes, which arrived with no more issues.
This is why in my next trip I am going to change the cabin suitcase for a big camera backpack, one of my partners use to travel with this bag with no issues untill now, nobody looks at the backpacks hanging for your back and if they do they assume it's not that heavy.