I don't think legendaries should be trivialized at all, being able to reserve it does just that and do remember that not any normal trainer can ever own one, you can only own one in the games because it's the bloody game and the entire game world revolves around you in it. "If you want it, you have to earn it" sounds much fairer.

As in, make the entire ordeal incredibly difficult anyway, and make any mistake the trainer makes punished at least 3x harder than if they were doing a normal battle or capture.

Also you should probably put the character sheet details in the first post too.