When it comes to a usb flooppy emulator, there is no obstacles concerning drive's rpm, hall sensors,timing of motor step etc.
I kind of "prove" this my self, by testing the 68000/14Mhz hack on my A500. Using a real drive didn't work because of the double speed of "E" signal which drives the I/O CIA chips, that affect all the electro mechanical signals of the floppy. But when i tried using gotek, it worked fine!
So what i'm asking is, if the way to achieve double speed on a usb floppy emulator ONLY (and not a real drive where much more issues emerge), is changing some settings of the gotek firmware, or there is an "unbeaten" limit of the max speed paula can encode/decode mfm data stream!