>>33207846nowhere is it said that the E4 HAVE to be the current Kahunas. If anything, the way it is now makes the story of a makeshift Pokemon League much more believable. It's just an old tradition that the Island Champ has to face the Kahunas in the end of his journey. Kukui was inspired by that tradition and tried to get as many Kahunas in the boat as possible but improvised on the rest. Makes sense to me! Anything else would be stale and predictable imho.
Kahili isn't even a no name, her story is just not rubbed in your face! Just like it was with all the elite 4 up until now.
She was mentioned in the sm demo, and we can even assume that she has some kind of connection to Guzma who had a golf career on his own at some point. I'm certain we'll explore this ark even further in USUM (or the anime..). I find this kind of story telling much more appealing.
Furthermore, Hapu was JUST named Kahuna and was more interested in becoming the champ herself (thus her title defence battle).