That's why I said ARM for the EBS protocol handling rather than MIPS. :-)

I guessed a hardware NVMe interface because that seems like something which could be acquired more or less off-the-shelf, thus minimizing the engineering risks.

I do, hence my speculation about putting the NVMe in firmware instead of hardware :)

(Colin's speculation in a peer reply is also reasonable -- personally I've seen enough errata in "off the shelf" IP to shudder at the idea of anything in silicon that doesn't have to be, but fundamentally I'm a SWE, so that would be my take, wouldn't it)

The way I see it, everything has errata... but if you're taking something off the shelf, it's more likely that someone else already found them. :-)