Put yourself in the game!

So I had an idea, it's the tropics, it's so lovely!

Can't think of a route, still haven't played, but why not put a yacht on a water route? Have a Rich Boy, and his two butlers. It's worth landing on the ship and defeating them, because once you do, the Rich Boy lets you visit below deck. On the deck there's a big nugget at the front of the ship, and you get on in back. Below deck is his girlfriend, a Lady, who can sell evolution stones, one of each per day.

Name: Winston & Alfred
Trainer type: Butlers
Saying before battle: "Oh! Are you a guest of the Young Master?" "Oh! Are you a friend of our Young Mistress?"
After, if you lose: "It seems this ruffian is not!" "Leave this vessel immediately, boat crasher!"
After, if you win: "Welcome to The Fat Lapras!" "Enjoy your stay!"
After, in the overworld: "Do you need anything? Refreshments or a snack?" "We're happy to serve guests, come again.
Pokemon you want on your team: Chyinmunk and Tancoon

After you win, the Rich Boy stands in front of the stairs/ladder down. If you try to sneak past to the Big Nugget, he shouts for you to come over.
Name: John Preston
Trainer type: Rich Boy
Saying before battle: "Ah, so someone found my Yacht again, well, if you can entertain me you can enjoy all this ship has to offer!"
After, if you lose: "A shame, well don't worry we'll get you to shore"
After, if you win: "Congratulations my new friend!"
After, in the overworld: "Enjoy the ship, oh and see my love below, she is quite the catch!"
Pokemon you want on your team: Felunge, Quetzoral, Empirilla

Now you can go below deck of The Fat Lapras. The Lady is blonde.
You can buy evolution stones from her, and she may call you rarely for a short time limited sale. She collects stones, traveling with her boyfriend to see sites and buy them. Sometimes she has too many, and will sell them at half her normal price. A different call is made when she wants a good battle, and after will let you pick a rock for free, or a rare item (like Unova Artifacts or a special Evolution Item)
Name: Carrie Bradshaw
Trainer type: Lady
Saying before battle: "Oh you beat John? You'll definitely entertain me!"
After, if you lose: "I guess you aren't worthy of seeing my collection."
After, if you win: "Haven't battled this good since a meeting with the girls!"
After, in the overworld: "Wow, you beat Mir Large and me! You definitely deserve to hang out with me!"
Pokemon you want on your team: Whimsicott, Inflageta, Harylect, Glavinug
So yeah, she may talk about writing a column "Love and The Capital" in Castelia City. She and her 3 friends hung out, talked about their hobbies, and she met John Preston, or Mr Large. She plans on getting married to him soon, and hosting it in the Tandor Region.
She'll sell you the original evolution stones, and after your first rematch sell you the rest.
Talking to John Preston, you get to learn about their slow burn relationship, and how he gained his Empirilla's Jungle Crown. If you get to know them both well enough, and you the devs wanted to, you could do an event that is their wedding, where you get to battle wedding guests, get party favors, and even battle the couple, all during the reception after the ceremonies. I'd be happy to write up the event, and trainers if needed.

If you guys were up to making a new trainer type to add some diversity or whatever, you could make some more Pirate and Ninja Trainers. Ones like Pirate Girl and Pirate Boy, along with

Name: Annie and Ryuko
Trainer type: Impossible Duo (Pirate Girl & Ninja Boy)
Saying before battle: "You're looking at the next Pirate Queen, now walk the plank!!" "Any future Ninja Lord can't let a witness live!"
After, if you lose: "And another walks the plank!" "And another witness eliminated!"
After, if you win: "Ouch! Don't keelhaul me!" "I didn't see anything!"
After, in the overworld: "I'll make you walk the plank someday!" "You'll taste my kunai someday!"
Pokemon you want on your team: Frynai or Selkid and Costraw or Chimecal