I think I have misunderstood the proposal… I read it as wanting to add a new instance of vtkDataSetAttributes to each vtkDataObject rather than adding a new array role to the vtkDataSetAttributes class.
If that’s the case, my only hesitation is that now users will expect process IDs to be present or easily inferred. If you are proposing writing a general-purpose filter to create process IDs, that is great (although covering poly-data, unstructured grids, composite data, tables, etc. could be a challenge).