I had a problem today
I can use python and loop over all faces and recalculate normals,
but to calculate normals for just effected faces from a manipulation I had a issue.
How does one get all vertex associated with any faces associated with another vertex?
So, if I can do that, I can recalculate the normals very quickly (trying to sculpt with python)
or even a command that works in the bge and bpy
recalculateNormals(vertexList,True/False (BGEmesh / BPYMesh))