Actually, I found a way to do this and it WORKS beautifully. I'm loading ROMs and ISOs to my SSD right now and the performance is OFF THE CHARTS.
Here's what you need:
A SATA-to-USB converter (I use USB 3.0)
A software program to burn the image onto the USB drive (however, only certain ones will burn to HDDs, I used Etcher).
A HDD or SSD (obviously)
x86/x64 image of Batocera.
Personally, once I get this loaded, I'm sure it's probably going to become one of my favorite machines, if not, my absolutely favorite gaming machine I've got in the place.