In EDDW the minima are quite a bit higher than the corresponding ILS
Do you have the chart you are using for this procedure?
This is likely due to obstacles in the missed. GBAS is for the approach, RNAV is required for the transition to the signal and for the missed.
There are some entities using the GBAS CAT III autoland, the signal is already there, the FAA hasnt cert'd anything better than CAT I....
Currently we are working on complex GLS signals that will include curved paths. That should give the FAA something to gnaw on for a while.