The Elite Four should specialize in more than just one type of Pokemon, as they did back in the good old days.
>Lorelei was an Ice/Water trainer, Bruno was Rock/Fighting, Agatha was Ghost/Poison, and Lance was Dragon/Flying trainer
>Koga in GSC used Bug types, Karen used shit that was just "Dark" like Poison types
>Flint used whatever the fuck in DP
It makes them feel stronger than just being one type Trainers. That just makes them feel like slightly more dangerous Gym Leaders.