I don't understand your logic. We have 22 Fullart cards in the set. 10 or in your theory 12 Fullart Pokémon, so there will be at least 10 Trainer Fullarts, 5 per japanese set. I think, there would be a hint, if we would still have ex Pokémon, so there will be only 10 Fullart Pokémon and 12 Fullart Trainer, 6 per japanese set. 2 Items, 1 Stadium, 3 Supporter isn't unrealistic. But in your logic 5 Fullart Trainer = 2 Items, 1 Stadium and 2 Supporter could also be. I'm not sure about no Supporter Fullarts, but would it be so bad? Items and Stadiums Fullart and Supporter SARs would be interesting as well.