I can see floating about inside a ship only working with derelict ships, or if your ship is suitably powered down/disabled. Personally I wouldn't want it for moving about my own ship instead of walking about.
Throughout the development of the game some people have always complained x, y, z feature is missing from it. It's just the way it is. I can't imagine ship interiors not coming unless the game is cut short by FDev. It's really the 'missing link' between walking and piloting shops, and there's plenty of scope for missions that merge/blend both parts into a single mission. As with all things Elite related it will take time....