Merged FileSystem - USB for Games only?

[cursedverses]

Please feel free to ignore this, it's a bit of a brain dump.

I've been thinking about the possibility of having a USB device mount and share the same folder structure as the sdcard (think of how persistent storage works on a Live CD). Would it work if I had an SD card just for cores and ROMs, then a USB I could insert that would provide Carts/Disks/etc. For whichever system I choose to use...?

Is there a demand for this?

[AngelicLiver]

USB drive support was added over a year ago. If you retain the default directory structure on the USB device, when plugged in, MiSTer should mount everything to be visible in the respective cores menu. It is very straightforward and works flawlessly. I have a drive set aside solely for CD games.

So yes, you can have your SD card solely for cores and store your ROMs/images etc. on an external device. Cores look for files in this order SD > USB > CIFs.