I doubt that the costs of adding depreciated results to the standard will be greater than the benefits. It would make the standard more complex and more difficult to use. We do not use depreciated versions for other elements in the standard such as country and sector percentages, classifications like policy markers, sector codes etc. Why make an exception for results?
If an IATI data consumer is interested in depreciated values of baselines, targets and actuals, the way forward would be to keep the previously published versions in a database. It is up to the data consumer to make this effort or not, depending on the functional requirements.
To accommodate the need to make transparent that values have been changed, in the current standard the result narratives can be used.