OVC002
IMHO this is an unlikely scenario. The UK PPL requirements dictate that a student must pass 7 ground exams, one of which is VHF Communications. The comms exam consists of the written theory, and also a VHF practical, conducted by an R/T examiner. I suppose that it is technically feasible, that a pilot could learn at a school in a non radio equipped aeroplane, but again, I feel that this would be somewhat unlikely today.
I know that someone will, in all probability quote the "I learnt in my own non-radio aeroplane, but these individuals are very much in the minority.
However, were your hypothetical flight to occur, the answer is still NO, your passenger with a FRTOL is still a passenger not a member of the operating crew. Operating crew capacity is dictated by the certification of the aeroplane. The fact that the pilot does not hold an R/T licence, merely precludes him from entering Class D airspace.
Having said that, would ATC actually know that the voice on the R/T isnt t actually the pilot flying the aeroplane. I think that this would perhaps only become evident if there were an incident or accident.
Anyway - thats my five pennorth....
Cheers