Because the Caravelle employs exactly the same floor rail system and the same three seater rear bench seat as the Beach, there are numerous possibilities available to you. However, I'm not sure if you will have a multiflex board bed extension. If not, one of these may prove a useful addition to your van. However be sure to get the higher split folding version as fitted in the Beach with the three seater Beach. It's designed to provide the right height support in the rear for the bed when the bench is folded down to provide a double bed. It also allows for greater storage flexibility in the boot and because of it's spilt folding element, it increases your seating and leg room options in the passenger compartment. You'll also need the VW Comfort mattress which irons out the undulations in the folded bench to provide a perfectly flat bed. Here are some options you could consider:
1. There are number of companies that specialise is making excellent removable pods with or without a stove, sink etc etc. There appear to be many permutations of this pod theme so you should find something that suits you. You may be aware that I have a seven seater Beach and that personally don't favour the pod approach. My only reason for this is that a pod would reduce the available space in the rear passenger compartment. That said, there are some brilliant professionally made pods that may suit your needs well.
2. There is also the ready made slide out boot kitchen to consider. These units are very slick and I believe they can be ordered to your specification and colour to match your van. These kitchens can be used either extended out under the tailgate or removed from the vehicle and used as a stand alone unit.
3. Or you could try the modular approach with a kitchen stored in the boot on a pull out tray. This is very much the DIY approach but it does enable you to design your own specific storage/kitchen solution to suit your own specific needs. A number of members have designed their own storage systems along these lines, some with and some without a pull out tray. Personally, I think that the pull out storage tray is a real game changer as it makes access to everything simple and easy.
Here's a snap of my system:
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@Amarillo has another interesting alternative but in the end it's down to you to decide what works best for you.?