What if a docking accident leaves the spacecraft depressurized and unable to re-pressurize. The hatch may be jammed/ punctured or a window blown. In such a scenario, the astronauts would have their pressure suits on. They would be unable to dock, or abort & return to earth.
They could only survive if they could do an emergency EVA to the station's airlock.
Do the Dragon or Starliner pressure suits have that functionality? Could they shut off and detach the umbilical and use a small emergency air tank like divers have? They are not EVA suits, so they lack insulation and other features, but one would imagine they would be adequate for the few minutes it would take to save life.