Ummm, I think that the use of reduced thrust (Assumed Temperature / Flex) puts the aircraft in a (close to) performance limited Takeoff in each case. With a very large thrust reduction, the trainee is seeing the aircraft perform just as it would at maximum weight for the prevailing conditions. Speeds would, of course, be lower, but even in day to day light / heavy Takeoff Weights, we see large variation in Takeoff speeds every flight.
Granted, a light Vs a heavy aircraft may exhibit different landing characteristics, but the basics are the same.
Apart from trainees and some refreshments, the only load that we carry is ballast, as empty aircraft are notoriously out of trim in the unloaded condition.
Regards,
Old Smokey