It will be very interesting, in fact Green and Silver in the manga are actually siblings and are son/daughter of Giovanni, and it will be interesting at the height of this Gen 7 of Giovanni makes an appearance (in person) like he did in Gen 5 anime and somewhat relate to Lillie's mom.
Actually Green and Silver are unrelated. While Silver is Giovanni's son, him and Green (along with a few other kids) were kidnapped by the Masked Man to be his elite servants. Both Green and Silver formed a brother-sister bond, helping each other escape which eventual leads to their stories in the manga.
I hope they realize the anime needs to be bigger than the games, the darker story in the games should be expanded upon, rather than casually covered in the anime. If the anime is supposed to support the games, let it showcase the intricate stories, while also adding newer or different elements like the fact Team rocket and ash are in it.
Oh, they know that the anime will probably run out of material if they follow the games, filler is a give-in after all the planning is made and they see where there's a gap that needs to be filled. But the problem is the writers have little to no interest to the game's plot and go off to making their own story which for the most part feels disappointing compared to what the games gave us. Now to be fair, with Hoenn, Sinnoh, and Kalos there's really wasn't much about the villains your could do from the games so it was okay if they kept their story on the backburner and not having Ash & co. encounter them as much as you did in the games. In addition Hoenn and Sinnoh did have something close to the game's ending point for the villains. However they dropped the plot ball hard with Gen 5, they completely missed the point of Team Plasma. Then when they had to cancel Plasma's debut episode it completely derailed whatever story they made for them and had to throw in a Team Plasma arc AFTER the Pokemon League. Kalos didn't fair any better, Team Flare also essentially pushed to after the league and what their plan is has nothing to do what the games had (instead of Lysandre's plan to cull & genocide with the Ultimate Weapon which also brings in AZ's story, instead in the anime Lysandre wants to take over the world using Zygarde *yawn* ). And do we even need to mention all the interesting characters & locations in the games they passed over for their own, many being character/locations of the day and only a handful being interesting (though still not the character from the games you wanted to see).
And most mind-boggling about this is Pokemon Generations was made by the same people as the main anime (but obviously with a budget). HOW?! And I'm not asking for Pokemon Generations level animation here, what I'm asking is for Pokemon Generation level storytelling. Because even if they did change some things (though you could blame that on the them being short episodes), I still saw characters from the games I wanted to see in situations similar enough to what happened in the games. Why for the short series you stayed "loyal" while for the anime you completely discard most everything even though in the anime you had more room to develop the story?
Now it's too early to see what direction Alola is heading. The notable changes so far is that Lillie doesn't have Cosmog, Gladion doesn't have Type: Null, both aren't runaways (at least not Lillie), Hau is a no show, and there doesn't seem to be trail captains (though the Captains are appearing in some capacity, even Ilima is appearing soon despite his Trial being done with). That said, since nothing much happens on Mele Mele they could be using it to do most of the early character development before diving into the story starting with Akala.
Would you guys want any previous characters, big or small, to return to the anime?
How would Misty fair? Getting to ride Lapras and make use of the island setting to let her water Pokemon swim and snorkel.
What about May or Dawn? No contests, but maybe Trials would pique their interests...
Iris, her character is so independent of any real premise she could be anything here. But notice I said premise not purpose. Her purpose is to move up the ranks as a Dragon Master, like Misty's is a water Pokemon Master. Her purpose in Alola besides catching more Pokemon is up for anything. I don't even see her traveling to Alola hoping to see Ash, I think it would almost be like she runs into him because she is already there. She literally looks like the next trial captain! Why isn't she here?
Serena, unfinished business, to say the least, could give audiences closure on her final "interaction" with Ash, but maybe leaving it unresolved means it won't risk being ruined by revisiting "the moment."
Brock? He seems almost too old, but I could see him going crazy over Alolan Golem.
Tracey, he is probably going to want to catch some Pokémon that has a search feature... hmm. How about Pokedex Rotom?! That would be the perfect partner for Tracey, and would support Oak back home.
Cilan? Maybe he could cook up some... plot points? I doubt it. I can basically say he is a step up from Tracey, but in a category of supporting role without being necessary. I guess cooking gives him something over Tracey.
Clemont? The islands don't seem to want Technology, besides Rotom Pokedex. What would his inventions serve a purpose for? I could see a small arc on his studies and attempts to join the Institute, but failing miserably and then feeling like he isn't good enough. The final part of the arc is he realized that they wanted him to fail so he wouldn't uncover their secrets... Does he get to tell ash and friends before they stop him? Will Bonnie be there to save him in a surprise cameo at the last second? Stay tuned and find out!
Sorry Brock, Tracey and cilan, it seems at least Clemont found a purpose!
Max / Bonnie? Only if they actually did something.
My vote goes for Iris & Serena, since they deserve their post series cameo that Misty, May, and Dawn got. But let's look through all of them for the heck of it:
Misty: Misty is one of the my favorites (and yes, I'm Gen I bias/Pokeshipper :P), but I don't think she needs to appear. Would be neat, and Kanto & Alola have a close connection so wouldn't be crazy for her to go there to maybe get some of the new Water-type Pokemon for the Gym. However I would much prefer to see Misty visiting or phoning Ash after a League when he comes home to Pallet to catch up on things.
Brock: Same with Misty, though I do agree with
Frozocrone that it would be hilarious to see Brock meeting Olivia (especially if the keep the game's part about Olivia looking for someone who isn't intimidated by her being a Kahuna). I don't think Croagunk could inject enough non-lethal poison to tame Brock. As for why Brock would be in Alola, well probably for doctor reasons. They could easily BS that on an island there's a plant which has powerful medical properties and Brock wants it for some reason.
Tracey: Eh, neat but don't think many would care (not Tracey's last cameo had him standing in a background of a video doing or saying nothing). Professor Oak could need to send something/get something from Samson so sends Tracey to deliver/receive it, so no problem getting him to Alola.
May/Dawn: These two are more difficult to get over to Alola. Alola has no contests so only reason for them to go is I guess vacation/visit Ash but overall I don't think it's necessary.
Max/Bonnie: They're with their family, helping at home for one day they can get their trainer license (even though we've seen trainers their age and younger) so I don't think we'll see them again.
Iris: Iris got shafted of her cameo last gen with no reason. For where she could appear, well we do have an ancient Dragon Trial.
Cilan: Well Cilan likes fishing and there's plenty of that to do in Alola so I guess he could appear and would be nice to see him (even better if he just so happens to be in Alola the same time as Brock and they both realize they knew & traveled with Ash).
Clemont: While not stuck at the Gym as say Misty, still he has responsibilities in a region far away from Alola. That said, considering Ash has yet another Electric-type technological genius as a classmate, Sophocles, they could maybe have Clemont appear for some kind of genius/technology convention that's being held in Alola.
Serena: I would be surprised if Serena doesn't appear for her cameo. There's no reason for her not to, granted she's also suppose to be participating in Pokemon Contests to better train to be Kalos Queen but she's not trying to be a Top Coordinator so wouldn't be a big deal if she didn't make it to a Grand Festival.
Olivia is pretty fantastic to watch on screen.
Couldn't help but notice some funny little changes with Olivia:
Gee Olivia, you look more dressed than usually... and flatter.
Also she uses a Lycanroc Midday instead of a Midnight. I guess that's because Gladion now is using a Lycanroc Midnight and Kukui doesn't have a Lycanroc Midday in the anime. And once again Ash's Rockruff gets some attention showing it bonding with Olivia's Lycanrock Midday. They're really pushing on the mystery of, if Rockruff, which one would it evolve into (leaving me cautious of whether it won't evolve or they give it a third evolution form (we'll see what Ultra Sun & Ultra Moon brings to the Rockruff family, which we know they're doing something as we saw a Lycanroc Midday in the sneak peak trailer)).