Would probably just pressure wash the wall and consider the staircase. Maybe granite cladding on the steps would enhance it.
Don't think you can just plaster straight away either. Possibly if you apply a layer of facade insulation for plastered facades, and then mesh. Then the insulation can absorb certain movements. But I'm far from sure that such a construction would hold. Probably also requires ensuring that not too much water gets in from above, to avoid frost damage to the plaster.
Maybe it's easier to just build a new wall instead...