That interior design is almost perfect apart from one thing. The driver-side AC outlet is enormous! They should have thought it through and consider possibility of integrating digital rear view mirror screens into the design. That's a missed opportunity.
They did probably think it through... for the GS. I guarantee you that the entire black plastic form from the left vents to the screen on the right looks like a hack job because it was one to some extent.
If I had to guess:
It was going to be an early implementation/move towards large, possibly non-standard form factor screens (see their concept cars), that double as digital side mirrors.
Given the quality of execution in the design elsewhere, i just can't see those same designers thinking hey, we need an H20 button and a vent on the left, maybe we should make a giant, oddly shaped, underutilized slab of vertical plastic to your left.
That area was
obviously intended for something else to begin with. There's no reason for the vents to need to be on a perfectly flat, mostly vertical surface that mirrors nearly perfectly what's used for the center display. They could have just taken the design from the right hand side, and mirrored it I have a feeling they were going to try and do some interesting stuff with their displays in the GS, but cut and simplified components for the Mirai.
What an absolute waste of a good car. Absolute waste.