It would be very useful to completely exclude cargo bay doors and simply have the bottom half. I'm thinking mostly about making the ramp at the back of a cargo plane.
This. I was going to suggest a 'fuselage' or fuel tank part that was hollow, but I think this would be easier to implement for the devs, it could just be a tick box in one of the settings for the cargo bay.
This would go great with the implementation of the other suggestion for more customized cargo bay dimensions.
@Mod Ba dum thats a bad pun tsss
Now this is a suggestion that could hold some value.