I hate my MBWEII. I am one of the unfortunate people in which this device did nothing but cause headaches so I'm not all that sad about it's demise. Is there a way to basically use this as an external USB hard drive that will access both drives. Reviving this device as intended is not even a thought. Unfortunately, I'm pretty computer hardware/software literate when it comes to Windows OS (I know, it's sad) but have only dabbled a little into Linux.
I don't think that is possible with the MBxxx range of machines.
The MBxxx are all single-purpose computers designed to accept requests on the network and serve those requests with data from the hard drive. Making direct access to the hard drive is a completely different thing.
(For the same reason - I can write and read encrypted file containers on the box, but I can't "mount" the encrypted container to access the data within it, because that requires access at the hardware level, not at the file level. I have to copy the file container to my local system, mount it, edit things, close it, and copy it back to the MBxxx. Which is how it's meant to work.)
It's not logically impossible to have the computer also function as an external hard drive. But I don't think that the MBxxx do that.
I recall having a NAS device (Network Attached Storage) in the past that could be accessed either as a file-box on the network, or as a USB external hard drive ; it was about 1/3 of the cost of the MBxxx, after taking into account the costs of the drive itself. And it did none of the other things that an MBxxx can do, even before hacking it.