> We want well documented access to the low level device features.
> Any address-translation-layer should be optional at most.
Indeed. To rely entirely on wierd vendor firmware to decide what to do with my data is to be locked in to the vendor for updates. Even very good firmware can't predict new situations which will come up. And the freedom to try new ideas and models is a great thing.
Also, to put on my paranoid hat for a moment, not having a large translation layer also reduces the surface for malicious stuff.