Rob, I'm still trying to understand why you think that a vast amount of work is still needed. Do you agree that, once USB is available, the system is in a workable state? Do you think adding audio support is much work? What would you class as a "maybe not ideal, but it works" state?
Speaking of SD cards, I only ever read the spec of the wear levelling employed by SanDisk, and this is 100% compatible with FileCore. Since they are cheap enough, I can't see a problem telling people "buy SanDisk SD cards instead of the really cheap stuff". With prices currently at 30€ for 16GB for the UltraII cards, it is really cheap enough. If there is really a problem with FileCore on SD, just use DOSFS/Fat32FS as the default FS. Problem solved. Or else, use USB mass storage driver to connect a real HD. Problem also solved.