[jfrunyon]

Could be additional cargo space. Airlines would be quite happy, they could accept more cargo = more $.

[Symbiote]

Look at the diagram on [1], it's a fairly small space. Other diagrams [2] suggest it's also a weird shape.

[1] https://aviation.stackexchange.com/questions/27419/how-is-th...

[2] https://www.smartcockpit.com/docs/a350-900-flight-deck-and-s...

[formerly_proven]

The extremely wide FoV in the video makes it look far bigger than it is.