I'm going to be as honest as I can with my comment. An average pokemon fanatic human in his right mind wouldn't pick legendary pokemons as far as just being able to summon them is fine. However, I will kindly remind you that a system is made to strengthen a host through rewards. If not all of them are like this, a Pokémon could reach its last evolution and give a power according to the element. An example is an ice-fairy type Pokémon would give immunity to cold and I guessed more handsome. It would be better that each combination of elements give different prizes and the solitary elements such as a Pokémon only fire is saved to be able to make a new Pokémon made by it by combining it with another element without restrictions, thus leaving room for the protagonist's imagination (PS; go to ua institute is repetitive but the best choice for a more fluid story will be easier for you to locate what you want to happen (no-haren is the best option for the protagonist))
