I like the idea of Dual PSU, especially for expansion and failover
Well failover implies each PSU can handle the full load and that isn't confirmed. Expansion is improbable given the dimensions of the chassis. To their credit HF used the available space pretty well. I don't see you putting another module plus fan/radiator/pump combo in there without extensive redesign. Might be an interesting project.
They may not include 2 large enough PSUs, but it looks like you could upgrade the PSUs to be big enough. Its hard to tell without hard numbers, or MPP/non-mpp