I agree with WJones. I did something similar. I left the toilet in place, but added a shelf right over it, and a couple more above that. They are all removable. Thus, you can add or remove the shelves as needed based on your trip requirements and bathroom utilization. Thus, when you need storage more than bathroom, or bathroom more than storage, you can easily reconfigure prior to your trip. In a pinch, such as heavy pouring rain, you can still use the bathroom even if configured for storage. Not convenient, but more convenient that trudging out in the rain in the middle of a cold night
IMO, its the best of both worlds.