Oh yeah, NPC's need to poop, too, don't they? In that case, I really hope that each E4 chamber as a private bathroom hidden off to the side somewhere.
And I hope the Gym Leaders get paid. I mean, we know they get to keep the cash they earn from beating Trainers (as we know Crasher Wake uses that money to help his community), but if Norman relocated his entire family just so he could start winning petty cash off of kids and teenagers, then I feel even worse for his wife. She's acts all sweet and calm, but if he really is earning so little, then she's probably operating a call service or something out of her living room just to keep the roof over their heads, No wonder she gives her kid an Amulet Coin...someone needs to bring home the bacon.
And as to the unfortunate connotations of a league being built that you mentioned earlier, I don't think it will replace the Island Challenge. As has been brought up, your character isn't the one actually bringing this concept with them, and odds are a league can't be forcibly built somewhere. I'm thinking that the leaders of Alola, likely the Kahunas, decided to have a league built as to compliment the Island Challenge, as Gyms (if we get them, which I think we will) and the E4 are there as a way to test a Trainer's battling skills, while the Trials serve as a way to test the bond between Trainer and Pokemon, which is why they don't always involve battling ("find me ingredients", "take some pictures", let's DANCE!", etc.).
Basically, I see the League and the Challenge as two separate options for Trainers to choose, similar to the Gym/Contest paths (only Trials are a full path, unlike Contests, which are just a fun thing on the side).