More specifically, the charger is located in the hump behind the back seat. A higher capacity charger will almost certainly be physically larger. Can it be configured to fit inside that hump? Maybe, maybe not. Rumor has it that Nissan isn't even going to try, and will relocate the larger charger to the front of the car. Can you imagine trying to reconfigure the "engine" compartment of an existing car to accommodate an additional component like that?
Not to mention that the charger is water cooled and uses some very hefty electric cables. The larger charger will need more cooling. Is the existing system adequate for that? Probably, but who knows. It will definitely need larger cables running back to it from the charge port at the very front of the car. Not only are these expensive, but will there be room in the existing channels for the larger diameter wires?
Of course it's doable, at a price. How many thousands of dollars are you willing to spend, and how many others can you find willing to spend those amounts so that there is a viable business plan for the product?
Ray