wb - you won't be able to get a removeable MD because fundamentally all MDs are slaves to the core.... in other words the core provides services that are needed for any MD to do anything, thus once removed (even if a disked MD) it will have no ability to do stuff.
As for sync'ing to removeable player devices like iPod, etc, yes I agree with Totallymaxed this would be a great feature (horses for course, far better to use that technology and use a tiny, cheap device like an mp3 player, than try to cludge the LMCE and have to walk around with a bulky, expensive MD!) This suggestion is already in the Features forum, btw, I posted it a long time ago, and a ticket in Mantis (don't remember whether I ever moved it to Trac, but probably not). I was hoping for something that would write a simple ID to each device you plugged in and declared a "sync device", which would then be used to keep track of the library entries that were to be synced with it. Then another 'sync' datagrid that would add 1) a kind of tick box to each tile that you could toggle for whether it should be sync'd to that particular device, and 2) a new sort mode that filtered for all entries that were ticked irrespective of folder location (as without this it would be difficult to get a full picture of the entries included in a large folder structure). And potentially, when the system's pnp detected a device with a recognised ID, it would kick you straight into that datagrid view on that MD...