That question should be directed to either Sven (@svenrademakers) or, if he can be coaxed to participate in the discussion, Sam (@CFSworks). Sam contributed the RockUSB support and knows how the RK1's loader works. It should be possible to flash it from the BMC. Whether there is enough space available in the BMC's 64MB (128MB ÷ 2) file system is unknown. I sensed they were struggling to get things to fit at times. If it was done via a bootable micro SD card image, there shouldn't be a space issue.