lets get some perspective here, page-7

Whist there are always challenges to increase the size of a plant, I can't see that there would be anything insurmountable.

Fluid beds are a well understood unit operation. You can get quite large units and the particle size under consideration is not unusual. Sand filled fluid bed furnaces are commonly used for solid fuel combustion.

The solid stream is a once through operation, without recirculation, so there shouldn't be any opportunity for the chemistry to alter unexpectedly. The acid is recirculated, but it would effectively be purified in the EARS step.

The leacher may alter flow characteristics as it is scaled up. It is an unusual shape, and flow through increasing diameters can result in things like short circuiting. I'd be surprised if this was unable to be worked through. There are many ways to skin a cat.

The materials handling part is bread-and-butter stuff for someone like BHP.

Whilst I have said previously that it is prudent to scaleup stepwise, I wouldn't be too nervous about the likely success of those steps. Just a matter of working through them.