I have the a6500 in a Nauticam housing plus two strobes, float arms, ports, CMC-2 lens, focus light, and accessories and my bag of choice is the Think Tank Airport Takeoff. It converts quickly and easily from a rolling bag to a backpack and it holds a ton. Yeah, it's pretty pricey, but it's built great and has worked for me for years. It's a bit too big when stuffed for under the seat, but if fits nicely in the overhead bin. Usually I roll it around the airport but switch it to backpack mode and throw it on my back when boarding...makes it easier to avoid having to gate check it.
Airport TakeOff™ V2.0
I carry the camera and two lenses in a separate small camera bag and my Nauticam WWL-1 in it's own case in a smaller rolling duffel bag I carry on.
Airport TakeOff™ V2.0
I carry the camera and two lenses in a separate small camera bag and my Nauticam WWL-1 in it's own case in a smaller rolling duffel bag I carry on.