It seems currently there is no way to remove a cursed item from an RSD once it is equipped.
RSD Brew "Hallowed" which confers immunity to curses does not help.
Resting, Which applies "Restoration" does not help remove the item (But does remove the curses negative stats until you try to remove the cursed item again, where the script runs again andit is reapplied)
The level 8 RSD Ability "Restore" which applies "Greater Restoration" and "Remove Curse" does not help.
Further, with remove curse not functioning on RSD's, it is to be the best of my knowledge functionally impossible to remove such an item.