RAM Super High Roof: In-floor bed?

Hi all, I've got an interesting requirement of storing 2 bikes inside a van with easy access. My idea is to use a Super High roof, and instead of the classic elevator bed that you can walk under, I want to do a raised floor with the bed hidden in the floor towards the cab, and the sitting/lounge area above it. Attached is a render of an initial idea, the bed being blue (and in the floor) in the render.

This means with a standard height kitchen counter in the back of the van, plus the 6" raised floor underneath, we get enough height under the counter to put the bikes. It also means a full ceiling for fans where we want them, room for recirculating shower in the kitchen, and other under-floor storage for heavy things like batteries.

The challenge is the bed, as with that large of an area, a cover would flex and dip when standing in the middle, and there won't be a lot of height to put cross beams if I want a 6" mattress. I'd also ideally want a way to "raise" the bed, but that's secondary.

Anyone have ideas for this kind of build? Also, any thoughts on if the Super High Roof narrows more at the top than a High Roof? I haven't seen one in person yet.