I would say, we use an Child->Parent attachment to attach the shuttle to the space station, when possible (Similar to Project Apollo).
When no such attachment exists, we just check the distance between the docking ports. When the distance gets closer than the distance between shuttle docking port and extended ring, the ring gets just retracted for avoiding strange looks.
This might be the best we can make of the situation.
Having a special ISS for SSU missions would be the best way to have the first way of docking I described.