Automatically reversible conveyor

I would like to be able to automatically reverse the direction of a conveyor when connected to a balancer.
For example, for the production of mechanical parts, I have a number of buildings that use mechanical parts nearby. (maintenance, for instance) I thus have conveyors leading from mechanical parts production to those other buildings, with balancers to ensure priority. I also have a storage so that if all other uses are full, the excess production of mechanical parts goes into storage. Lastly, I have a conveyor coming _from_ that storage, so that it utilization gets ahead of production, the storage will provide what is needed.
I think it would be useful to have a type of conveyor that when connected to a balancer could take the excess production to storage, but could also reverse and provide input from storage if there is insufficient input on the balancer.