I quite like the diversity available to us in Pokkén, despite almost all of them being humanoid and understandably so, which is why I thought at first that there is room for a very different type of fighter. And I thought while she may not be a fan favourite like most of the Pokkén cast, Altaria is definitely a candidate with enough personality and enough potential to be animated into a fluid and realizable fighter which is why I wanted to suggest the first of what might be a few hypothetical Pokémon choices for Pokkén.
Creates a static low-lying fog on the battlefield around Altaria which while in range, increases speed for Altaria, and decreases speed for the opponent. The opponent’s speed will not be lowered if the opponent already has a buff of any kind, in which case, the buff will removed. The mist can be shielded and if so, the mist will evaporate from the ground. This move deals no damage or hitstun.
24 Frames (Slow)
Designed with oki potential in mind
Mist created is similar in size to Aegislash's Sacred Sword mist
Cotton Guard (4A)
A counter move which grants armour throughout the entire move and upon blocking a hit, grants Altaria a defense buff for a small amount of time and health. Whilst useful, this move grants no follow ups even on activation and returns the battle to the neutral.
Frame 19 (Medium Slow)
Armour lasts for 20 frames
The defense buff lasts for 9 seconds
Sky Attack (jA)
Altaria glows and hovers in the air momentarily before unleashing a powerful divekick-like attack which pierces counter and is safe on shield (0) and knocks the opponent down .
Deals 120 damage
Can be angled forwards and backwards in duel and field, and also sideways in field to catch sidesteps and other movement
Altaria stretches out her wings and lets out a soothing call which deals no damage however puts the opponent in the crumple state, allowing Altaria to set-up a powerful oki or followup with a quick (frame 11) normal to reset.
Main 5YYY Pokécombo cancel
Reaches just far enough for the jab to be cancelled into Sing successfully
Only goes in front of Altaria
Altaria being a bird and all likes to be in the air which is why the widest variety of normals would come in the form of directional aerial attacks. Altaria also has a floaty jump which allows her to move slightly in the air similar to Chandelure and Gengar to better allow her to land her aerial combos and also to potentially cross up. Altaria's ground game however is quite weak meaning her speed on the ground is slightly inconsistent as she hops on the ground like some birds do and her grounded normals have slow startups, except for her 2Y (frame 11) which has no follow ups. This weakness is slightly made-up for in her unusual but useful Pokémon moves which can grant an array of beneficial scenarios for her meaning that despite her having a very different neutral game, she has the potential to be in the advantageous state for a long time.
Altaria is the Humming Pokémon which is why her idle could be a gentle sway of the head and closed eyes humming along to a tune. Her personality can be well expressed in her design, I think.
Mega Altaria wouldn't have too much change for her as she already has some powerful moves and good sustainability, however an extended combo game in the form of her Sing turning into Disarming Voice and launching the opponent into the air for a continued combo extension. Altaria's burst attack could be inspired from Perish Song and the activation could be an aerial grab. Her Burst attack would do 190 damage and grant a small amount of recoverable HP for Altaria.
Maybe a character as unique as Altaria might not make it but I would personally be thrilled, not because Altaria is a particular favourite of mine, but rather because I would love to see Pokkén's cast represent the wild diversity of designs that the Pokémon world has.
If there's anything I forgot or any questions/feedback, let me know!