Leaf pick up truck

This would be a coupe utility. They have been common (as factory models) for a long time, so there are many examples if you know what to look for... but only some manufacturers do them, and that generally does not include Nissan. Factory coupe utilities typically have a body like that Leaf conversion; a tray back is common on commercial vehicles, but less common on vehicles of this type sharing the front with a passenger car.

The challenge is entirely structural: keeping the required strength with no structural panels above the tops of the rear tires in a vehicle designed for full body. This is simpler if you keep the original wheelbase, but the vehicle would likely be more useful (depending on how you intend to use it) with a wheelbase stretch. That Rampage has a wheelbase 194 mm (7.6") longer than the Omni/Horizon on which is based; one of the few other similar vehicles familiar in North America was the Rabbit Pickup (Caddy elsewhere) which was 225 mm (8.8") longer than the Rabbit (Golf).

Both the Rampage and the Rabbit Pickup used an entirely different rear suspension from the corresponding hatchbacks - the same design would have worked fine but they needed more capacity and stuck in the cheapest possible hardware (beam axle on leaf springs) because that's good enough for a truck. It makes sense to keep the Leaf suspension, but within the load capacity of that hardware or whatever can be easily swapped in (the Leaf shares chassis parts with some other Nissan models).

Of course all of this has nothing to do with the Leaf being an EV... although if you have enough load capacity and stretch the wheelbase, you could possibly add more battery.