another issue with reversing the C5 is the pedals will also rotate backwards, so you could cause yourself a very severe injury
i did see a kit made that uses the C5 chain to drive the C5, this has a mechanism to disengage the pedals for reversing, but to be honest is that worth the cost and installation effort involved?
for me, getting out to reverse it is all part and parcel of the C5's eccentric charm, most use a C5 for a bit of enjoyment often as with this forum with like minded friends.