Why there are still no Pokemon in the role of trainer? What was the point of Oranguru's dex entry if we haven't seen him in action?

Remember that one Gillian in Espada? I always felt that there should be an odd one among gym leaders or elite four as well. Be it Ditto or Zoroark in disguise, or intelligent pokemon like Oranguru, Slowking or Alakazam. Or something completely different.