I think one of the advantages of FLS is that it's automatically temperature compensated.
RNP-AR is only designed for uncompensated Baro-VNAV....
The flightpath is already corrected for NA above and NA below...
it is dangerous to attempt to add temperature correction...aerodrome temperature is meaningless aloft...,
I dont see many aerodromes with compensated VNAV approach...what temperature would you be compensating for, the aerodrome temperature on the ground? or temperatures aloft?
the pattern would be a mess flying compensated and uncompensated approaches with the associated altitude differences...and min required separation
The only disadvantage would be the inability to use FINAL APP to perform RNP approaches, as previous posters have mentioned. From what I understand an upcoming MMR upgrade will eliminate that limitation.
Even if the ac can do it, I doubt if the pattern can monitor separation standards...
BTW...agree with Nick 1...