As mentioned here already and considering the above, we believe we should drop RFC-97 and do not continue with the related implementation.
Fast unbonding is arguably less critical for validators. In the future, we might want to consider enabling fast unbonding for a validator that has never entered the active set.
A related PR to implement nominators-related change for phase 1 is currently under review and aimed to be merged ASAP and deployed together with the other relevant changes for DAP / phase 1 by March if the related WFC is approved.