I realised you've already ruled out the full-size ipods as too bulky - but a thought that crosses my mind once in a while, is that given the number of aftermarket parts for 5G/6G iPods - I'm surprised no-one's come up with an aftermarket logic board.

My desired feature set otherwise doesn't differ too much from yours. Flac, BT for headphones, wifi to sync (from something that isn't itunes), support for larger sdcards, and maybe charging over anything but the 30pin. And then that one annoying bug - it'd be nice if 'shuffle all' didn't internally create a playlist that contained every song, creating an artificial limit on how many tracks can be used because that playlist fills the ram.

But what the full-size ipod really benefits from at the moment is aftermarket parts - chassis, shell, screen, touchwheel, batteries, etc. The logic board is really the only supply-constrained part left, and just addressing that one part cuts down the manufacturing dramatically.

Unfortunately the Nano doesn't garner the same aftermarket. Largely because it's dangerous & near-impossible to remove the innards once the battery starts swelling - so the biggest driver to rebuild it comes hand-in-hand with the inability to do so.