Except Incineroar is less fire actually. He's more of a brute attacker with wrestling motif, with fire on the side. And fire beam on your belt is one of the best ways to discharge fire.
Also Incineroar isn't a martial artist. Kayfabe literally his motif. And you seem to have a shallow viewpoint on Incineroar if you think he's all claws and such. Again, I've yet to see a pro wrestler in Smash and he has it in spades (with a touch of Jeeg).
My point isn't that Incineroar is only fire (as I point out later), but Fire is definitely one of the aspects of his design. I mean he literally is a FIRE type Pokemon, come on dude. And Smash has a LOT of fire attacks.
Mario, Luigi, Bowser, Zelda, Ryu, Fox, Falco, Captain Falcon, Ness, Lucas, Roy, Charizard, Olimar, Robin, Samus, Game & Watch and probably several more characters that I can't think of right now have attacks that involve fire in some shape or form, and that's if don't count explosions.
Meanwhile, plants are involved in Villager's moveset. That's it.
I didn't know wrestling wasn't martial arts, because as far as the definition goes, it's a "codified system or tradition of combat practices", and I would argue given the fact pro wrestling has specific names for specific combat maneuvers, that would classify as a "codified system of combat practices".
Martial arts isn't just Eastern Asian stuff. In fact, there's a
martial arts manual about Wrestling moves from 2000 BC.
Granted, this isn't modern pro wrestling, but it's wrestling nonetheless.
Furthermore, I didn't say Incineroar would ONLY have claw based attacks either. I said that since Wolf is a very possible returning veteran in Smash Switch, Incineroar would be not give
as many opportunities to be unique than Decidueye would, specifically for the fact that Wolf's Brawl moveset is mostly claws, and one of Incineroar's modes of attack would be claws.
Finally, you say there's no pro wrestling type character in Smash and while that is true, there are several characters who I would classify as "grappler" type characters, such as Bowser or Wario, who have command grabs and/or are clearly supposed to use grabs in their gameplay since they have good grabs and throws (Dedede comes to mind here in particular). And given how Smash's movesets work, it would be difficult to make a character who is more throw-based than that, since then you'd have to dedicate more than one special to be a command grab, and I feel like that doesn't work well.
Meanwhile, we have no character who is a pure archer who uses his bow for most of their moves like Hawkeye in MvC3 does. We have a few characters who can shoot an arrow from a bow in one single special move, but that's it.
Again, I'm not saying that Incineroar is never gonna happen. I'm just saying that I think he's less likely than Decidueye.