Klingon, I don't know where you got your nonsense from, but never were the terms 'navigator', 'air engineer' or 'loadmaster' ever used in initial FSTA work assessment - it was always Mission System Operator.
When researching FSTA skill sets, I asked a senior sqn ALM which of his specific in flight tasks couldn't be performed equally well by a senior steward. He couldn't come up with a single one - so the RNethAF KDC-10 'Operator/Loadmaster' concept looked a definite possibility for FSTA - with the cabin staff being all air stewards when needed for AT pax duties.
But if the navigators have now shown that they have more of the relevant skill sets, then I wouldn't be surprised at all. It's happened in other recent tanker types.
And as for your libellous comments about my attitude towards cabin crew, you can bloody go and get stuffed! Although I do recall having to persuade a certain loadmaster to stop mincing about and lend the MAMS people at hand at Freetown.... And another, at the same place, who was trying to find a rule to stop us taking a RFA matelot back with us, was told not to bother - the guy was coming back!