i did the that to my psr 1000 . it used floppies. so i bought and installed a usb floppy emulator. i used a 2 gig usb thumb drive. partitioned it into 99 1.44 mb partitions . now all my styles, registration, smf's are in one place. no more switching floppies. so in reality i only need (1.) 40 or so styles to perform (2.) easy access to midi files. so i don't really need alot. this seemed to work well for me on an old outdated machine.
I bought something from Russia for my PSR-2000 and PSR-2100 that did just that! It was some obscure thing, and I had to have a Russian friend call this guy long distance, transfer funds into this guy's bank, and then wait 6 weeks for the device to come. When it broke, he replaced it even though it took 3 months between shipping it and getting the other one back.
That's how I thought of this idea. I'm not enough of a techie to implement this idea, however.