Are you sure it's the hub being powered off and not the drive spinning down? It may be doing that itself in an effort to save power. My Western Digital drives don't do this.
I have been pushing for changes to memory playback that would prevent this interruption from happening, but the JRiver team seem happy with the new memory playback feature as it is. On my system, it's a serious regression from MC18. (much higher memory usage, ridiculous CPU usage, skipping during playback with it enabled)
What I would like to see, is memory playback going back to caching the file rather than decoded audio - at least a 50% memory saving right there - and use that freed up memory to cache the current and next track in memory.
That way you have the entire duration of a song to wait for the drive or network connection to become available and load up the next track, and playback should no longer be interrupted by things like that.