A proposal to reuse existing personal data should undergo an Ethics Assessment which is then signed-off by an accountable governance group that represents the organisation. This ensures that the management of an organisation is aware of how it is proposing to reuse existing data, and has an opportunity to challenge and embrace the ethics.
An ethics assessment will consider
Accountability
Fairness
Transparency
The Organisation may choose to publish its proposed reuse of data, and its assessment of the ethics.