Hello.
Thank you for sharing your project here! It is cool that you were able to get everything working.
I have added your app to the list of Wixel apps on the forum, and we are also planning on adding it to the Community Projects page.
Full speed USB is 12 Mbps (not counting all the protocol overhead), so I think the USB connection is probably not preventing you from making read and write speeds to be faster. I don’t know if this is possible or if you already implemented it, but it would be good if the USB transfers can happen in parallel with reading/writing data from the card.
For high-speed USB, there are probably some ARM-based microcontrollers from ST or NXP that can do it. It is unlikely that they would have a radio built-in though, like the CC2511.
I am not sure if it does high-speed USB or not, but the mbed acts a USB mass storage device.
–David