Warwick from SLRV is developing some rear drawer system, and that will include no doubt a fridge provision. Personally, I dont really see that a removable system is warranted, as it will be a killer to install/remove when you need.
Personally I intend to lay a drawer fridge next to a single 90cm deep drawer, and build some wings that extend over the wheel arches. That will make the top of the wheel arches the new floor level, which is fine as there is plenty of height left in the back still.
However, I will wait until I get it, so I can then work out exactly what to build.
Example of Fridge Drawer