So I was re-watching BW86 for the hilarious Wishfulshipping moment between these two, and the epic conclusion to the Gym Battle, when I started asking myself why Cilan and Iris had such weird makeups. So I went to look at them again. Then it hit me.
Oh my GAWD. Reshiram and Zekrom.
Reshiram is Fire/Dragon while Zekrom is Electric/Dragon. Reshiram represents Truth while Zekrom represents Ideals. Hitting you yet?
The reason why Ash has left Brock and the regional female player character behind in Unova wasn't just because they weren't popular enough, or that people were getting bored(although I admit, I enjoyed the change very much), but to grill the BW reference in even deeper.
Iris. She represents the ideals of the series of Pokemon, that she dreams to become a Dragon Master, and has the goal of rasing her Kibago into an Ononokus.
Cilan. He represents the truth that is seen in the relationships between trainer and pokemon, so I guess his sommelier stuff isn't all bull after all.
When you play the BW game, your two rivals are Cheren and Bianca, who represent Ideals and Truth respectively. You, the player(Hilbert or Hilda), are the one who is somewhere in between, something Ash is following pretty closely right now. If anyone's asking questions like why Cress or Chilli weren't chosen to be Ash's travelling partner instead of Cilan, I guess that they just can't fit the role as well as Cilan probably could. Same with Iris and Hilda.
Reshiram and Zekrom are Yin and Yang, just like how Cilan and Iris act for much of the BW series. This totally plays in so well I can't believe I didn't notice it earlier.
I see what you did there.