Very nice! I'm in the research phase planning for a trip similar to yours, also with a family of five. If you don't mind, I've got a few question!
Do you have some stats on your vehicle, like dimensions and weight? I bet you're pretty heavy with all the plywood, batteries and large tanks, but you're on a very good chassis.
From the research I've done, pretty much everyone I've read says to go small in Europe because of the narrower roads, low bridges, tight town centers, etc. You're rig is a very efficient use of space, but not small - how did that impact your trip? What are your thoughts on the tradeoffs between size and mobility?
Does your engine require Ultra-low-sulfur diesel and if so, were there any problems finding it on your trip?
The staterooms are what really make your rig stand out in my opinion. Very unique and it's not something that's easy to design in an RV given the space constraints. As I'm researching options for our own trip to Europe the most I'm coming up with is bunkbeds with the wife and I in a cab-over. I've also been looking at the new US navy style berths (see here for an example). Your stateroom are a cut above that. The only problem I see with your design is that there doesn't appear to be an emergency egress besides the main entrance to each stateroom.
Also, your solar system is very impressive. Do you know about how much power you used daily? With no propane, I assume the fridge and reefer are electric?