I finally registered specifically for this post. I would love love love to see a more boutique sff nas case. I currently have an unraid server at home that hosts plex, photo backup for my wife's photography, and general household archiving. In a perfect world for me a boutique nas would allow for 8 hard drives. Hot swappability not a hard and fast requirement for me - how often are we really swapping out hard drives and is it the end of the world to shut down a home server for 15 minutes while you install it? If I had any design skills I would draw up a model, but maybe words will be enough.
I envision a case laid out like the Dan A4, which has plenty of space for high performance mini-itx gear, an SFX psu, and PCIe Expansion. The difference would be I would just make the case wider to fit the 8 hard drives. I would also try and consider if there is a PCIe riser long enough to span from the MB, across/under the hard drives, and then end in a PCIe Bifurcation riser. The reason I would want a bifurcation riser is many ITX boards would require an HBA card to handle that many hard drives, and then another 8x lane could be used for a GPU for hardware acceleration in PLEX or in a virtualized PC.
I imagine something like this going under a TV console and potentially being used for combo NAS/TV Gaming PC.
I would pay money for some sort of expansion/extension for my existing Dan A4. I no longer have space for a desk so my beautiful case just sits in a box and I haven't found a purpose for it yet.