I think the additional overhead versus a docked system isn't as big as you think. The popular dock-based DC BikeShare requires a whole fleet of vans picking up

I think the additional overhead versus a docked system isn't as big as you think. The popular dock-based DC BikeShare requires a whole fleet of vans picking up bikes from completely full docks and redistributing them elsewhere. They finally set up a system where there's an employee waiting by a popular downtown bike rack to manually check in your bike because the rack would otherwise be full with a line of other people waiting for an open slot.