There's no cadets on the line with VA yet. Flights over approx 11 hours require augmented crew in order for the crew to get adequate rest. This is from EASA FTL Regulations:
(2) The maximum daily FDP under the provisions of ORO.FTL.205 (e) may be
extended due to in-flight rest for flight crew:
(i) with one additional flight crew member:
(A) up to 14 hours with class 3 rest facilities;
(B) up to 15 hours with class 2 rest facilities; or
(C) up to 16 hours with class 1 rest facilities;
(ii) with two additional flight crew members:
(A) up to 15 hours with class 3 rest facilities;
(B) up to 16 hours with class 2 rest facilities; or
(C) up to 17 hours with class 1 rest facilities.
There are no second officers or relief crews at VS, just First Officers who rotate roles on the long sectors which are mainly flown by 787s and A340s.
The MPL scheme is for the A330 only which is always in two crew ops at VS. So any cadets will actually being flying the aircraft in the RHS the same as any FO after the line training section is over.