Firstly: most current 777's have 2 ADF's fitted. However the next bunch of 300ER's at CX will NOT come with ADF's
Second: I'm pretty sure the 16 Twin Loc app in MEL is not in the Honeywell FMC database. You can build the legs if you want to and use L Nav ( monitoring the raw data for tracking ) BUT you cannot use Vnav for the arrival. Only Data base approaches can use V Nav for guidance. ( ILS's VOR/DME GPS etc all ok, there are no NDB approaches at all in a Boeing FMC )