I'm not sure but I think that the movements of the wheel are to fit in with the trip boat needs. When the trip boat goes up a narrowbeam can go with it and two narrowbeams or a widebeam can come down. If one caisson is used for other than boats the capacity is therefore reduced by a significant amount, especially for wide beam boats.
The policy of pre booking lock and bridge operation has already meant little movement on these canals, this will probably turn them into linear parks with some housing.