@E3roa
Palmer has a Dragonite because Palmer actually owns a Dragonite in the games. Right now this story is STRICTLY gen 4 in terms of Pokemon and moves, so there won't be any future generation Pokemon for a bit, that will change and it will be obvious when, but most of the trainers will still use only gen 4 Pokemon. As for returning Pokemon, well spoilers on who will be appearing to help Ash.
"Well this actually looks just fine." Ash said, looking around. "Maybe no one found the Pixie Plate yet or maybe it's not here."
"It's here, I can feel it's presence, and it's quite strong." Arceus said while in his human form.
"And with how the last one went, the only way for us to get the plates is by beating who or whatever has it in a battle." Ash said with a groan.
"Yes, it would seem so." Arceus said.
"And what was with them all being watery, and his Rhyperior was bigger than Groudon." Ash said, trying to figure out how he'd handle another 16 of these.
"It seems I misjudged just how much my plates would corrupt someone that came into contact with them." Arceus said.
"And you're sure the one plate we have is safe?" Ash double checked.
"Not even MissigNo could obtain the Splash Plate while I am in this form." Arceus said calmly.
"But you also can't fight in this form if we run into MissigNo." Ash countered.
"The plates are our top priority, without them this entire realm is doomed." Arceus said. "Are you sure you don't wish for assistance, we could ask…"
"No, whatever is thrown our way, I can handle, just like I did Palmer." Ash said angrily.
"This doesn't seem right, but I need us to keep alert to any strange goings on." Arceus said.
"Well let's look around the city it shouldn't be too hard to spot whatever has your plate, right?" Ash asked.
"There would be tell tale signs of it even in the early stages of being in possession of the plates, I'll know it as soon as I see them." Arceus said calmly.
"Ursaring, use Slash!" A voice called out.
"Now that sounds interesting." Ash said.
"Ash, we need to focus." Arceus reminded.
"We need to look for something strong and dangerous, if an Ursaring is battling, that's a good place to start." Ash said, running to where the action is.
Ash and Arceus ran towards the battle, seeing an Ursaring taking out another Pokemon.
"What is that Pokemon?" Ash asked.
"It's called a Kricketune," Arceus said, "but an Ursaring seems a bit much for it."
"Well, no point in him having all the fun." Ash said, leaping over the railing. "Hey, whoever you are, I want to challenge you to a battle."
"Hmm, and what's your name?" The boy asked.
"Ash Ketchum." Ash said calmly.
"I've heard of you, the unchallenged Frontier Brain." The boy said. "I'm Paul from Veilstone city, so sure, I'll challenge you."
"One on one sounds good, I'd like to see you fighting with that Ursaring." Ash said, grabbing a Pokeball.
"Fair enough, but I doubt you'll have an easy battle against me." Paul said.
"Snorlax I choose you!" Ash called out. "Use Mega Punch!"
"Ursaring use Hammer Arm!"
The two normal types slammed their arms into each other, pushing back and forth against each other.
"Snorlax use Mega Kick!"
"Ursaring use Bulk Up!"
Despite his massive weight, Snorlax leapt at Ursaring, feet first pushing against the large bear Pokemon.
"Snorlax use Focus Punch!"
"Ursaring use Focus Blast!"
Snorlax punched the orb of energy dissipating the Focus Blast that had come from Ursaring.
Arceus watched the match unfold from above, he could sense the Pixie Plate nearby but he couldn't see it or it's effects on anyone down there. The boy Ash was fighting seemed like a trainer as normal as any other.
"Snorlax use Mega Punch!"
"Ursaring use Slash!"
Snorlax punched Ursaring, sending the bear skidding backwards across the arena before standing back up.
"Ursaring use Hammer Arm!"
"Snorlax use Ice Punch!"
Snorlax's fist collided with Ursaring's arm, covering the normal type in a thick layer of ice.
"It's been a while since I've had a regular battle like that, it was nice." Ash said, shaking Paul's hand.
"No wonder no one can get to challenge you, if you're this tough Brandon has to be just as tough." Paul said with a smirk.
"And then some, but hey don't give up that Ursaring of yours is strong, and I got a few lucky hits in, I'm sure this won't be the last time I battle you." Ash said.
A bit later back with Arceus
"I Don't know what to tell you Arceus, the I can't find the plate anywhere." Ash said.
"I'm certain I sensed it during your battle." Arceus said.
"Paul wasn't corrupted like Palmer was, maybe it's still hidden beneath the arena, let's focus on finding others for now." Ash said. "So where to next?"
"The next closest plate is in Canalave City, an island to the west of here." Arceus said. "As well as being a dead end."
"So go there and turn back around." Ash commented.
"That was my plan." Arceus said. "Perhaps even stop and see an old friend on the return trip, they might have something that could help us in the future."
"You heard him Charizard, let's go!" Ash said as they took off towards Canalave City.
On the other side of the city
"Yes I know you granted me these powers of the Pixie Plate." Paul said angrily. "No he didn't have the Splash Plate with him, I don't know where it is."
The figure Paul was speaking to screeched an ear tearing noise, causing Paul's entire body to shimmer pink.
"Of course we'll keep an eye on him, that plate has to be somewhere." Paul said, as an oversized Infernape with pink flames appeared behind him. "Your word is my command my lord." Paul said taking a knee with his Infernape and Ursaring. All of their eyes glowing pink.
Ash's Current Team and Their Moves
Pikachu: Thunderbolt - Quick Attack - Iron Tail - Volt Tackle
Charizard: Flamethrower - Dragon Pulse - Air Slash - Seismic Toss
Sceptile: Leaf Blade - X Scissor - Night Slash - Double Team
Snorlax: Mega Punch - Mega Kick - Focus Punch - Ice Punch
Current plate locations
With Ash and Arceus
Splash
With Paul
Pixie
Unknown
Draco
Dread
Earth
Fist
Flame
Icicle
Insect
Iron
Meadow
Mind
Sky
Spooky
Stone
Toxic
Zap