Re: A new shift concept for the engineers....
i was thinking about that, too. with a freewheel you'd need to pull start it.
the main reasons for a freewheel are to set up your pedals for corners, stops, etc, and with multi-geared bikes, deraileurs don't work when pedaling backwards, so they don't work with a coaster brake.
weight is another reason. internally geared hubs and coasters weigh a lot more than what's essentially a front hub with a gear(s) screwed on.
it would be awesome to have a freewheel for coasting down hills, so your chain's not slapping around, but if i had gears, i wouldn't need to coast down hills...