Ability: Ball Fetch
New effect: If the Pokemon as no held item, and one has been used, it will gain this item. Basically Pick up, for SIngle. And Recycle, as it can be an item you used right before. An item that has been knocked off can return using this ability. Should it be limited to once or not is up to balance.
Competitive Reasoning: Well, it's like having a permanent item, for the cost of none. You could have multiple Ballon, focus sach, berry, etc... And that's it. Yamper doesn't have any way to throw an item, or switch his own. would be nice. Other than that, Ball Fetch is still definitively still niche
Thematic Reasoning: It's a dog. It doesn't need to fetch me only balls. Now go, Gunther! Fetch me an Iron Ball!
Ability: Keen Eyes
New effect: With it's imparable vision, a Pokemon cannot miss. Rather than just having a immunity to precision reduction, it just cannot miss. outside of OHKO moves, obviously. it also add Infiltrator in it's effect.
Competitive Reasoning: Basically a one-sided No Guard, that can pass through substitute and walls. Still a very niche ability, Certainly more efficient for pokemon that can't just phaze a Protect+Sub. I think it's practical for a wall breaker?
Thematic Reasoning: Well, the vision of these pokemon are locked on their opponent. Considering most of the inspiration for those pokemon are predators, they wouldn't let their avoid their attack. That's about it.
Also, I know the original talent ignore the opponent's evasiveness. It can just be the original effect, with Infiltrator as a bonus. I guess it could also act as a Pursuit erzacts, where a super effective move will hit it first, whenever a Pokemon is switched out. I kinda like that more than what I said before. But I don't know how to integrate it, nor if it's too strong
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Ability: Vital Spirit
New effect: The Pokemon have so much energy, it can never be put to sleep, neither does his opponent.
Competitive Reasoning: Fairly straight forward. It can block Rest. A pokemon with the Comatose Ability is considered awake, until the pokemon with Vital Spirit left the battleground. It's basically a permanent Electric Terrain, without the boost of the terrain, and only until the Pokemon switch-out. Proper prediction could severely punich Rest user.
Thematic Reasoning: Since Pokemon with this Ability are also the one who wants to have all your attention, it will refuse to let you sleep until you gave it what he knows you want. Hyperenergetic level of annoyance, dare I say.
We could extend to healing moves. But that wouldn't make sense. However, we could make it do damage each turn on the terrain, like a awaken, weaker Bad Dream. 1/16 damage seems fair enough, it's the amount of a Leftovers. on a single turn.
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Ability: Liquid Voice
New effect: Sound-based moves add the/become Water-type, and gains 1.3* power.
Competitive Reasoning: Once again, fairly straight forward. If we make Sound-Based moves gains the Water-type, it would be like Flying Press, and while Ghost would still be immune, it could allow some funny shenanigans (in doubles, so it will fall off here). If we make sound moves become Water-type, getting a slightly stronger move is always good.
Thematic Reasoning: Well, Primarina is said to have a very melodious voice, one that apease spirit! That's my only defense.
"When a Pokemon use a sound-based moves, it reduce damage by half", or "gain a stronger Aqua Ring, healing 1/8 H, thats protects from burn and heals on-going effect" could be considered to add to it's power. the first one following Punk Rock model, but it doesn't really fit Primarina's concept, which is more like a classical songtress. That's why I'd rather give her a stronger Aqua Ring, that heals status, like Rest can. Although it does work more like Shed Skin, clearring status each turn once active. 1/16 is alright, but as she doesn't have any healing moves. Also, you can't use the two Aqua Ring, for obvious reason (1/16+1/8, let's just leave that to Leftovers).
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Ability: Rivalry
New effect: If a pokemon have faced an opponent multiple time during a match , it will gain 1.3 power to his moves, and resist damage by 1.1. If the rival is faster than the Pokemon, it's considered as if they have the same speed, while no change as occured in their speed. The ability trigger when a Pokemon with Rivalry face the same opponent two time at least. 1/10 damage are received by the user each times it use an offensive move when the ability is activated.
Competitive Reasoning: I definitively went a bit wild on that one. We can just keep what's underlined. The rest is just here to help their bulk and their speed makes a speed tie where there's none. This part is definitively very a bit broken, as it does leave to RNG who will hit first (outside of priority move, that is), while giving strong advantage to the user, only when he faced a the same pokemon on the battle (gimmick that seems very exploitable). Otherwise, it's like having a second Life Orb as an Ability, which can be problematic, as you want to revenge kill with this. Someone with which could really help them, certainly.
Thematic Reasoning: Well, the rivals in game are as determined as you to become the best of themselves, and theypush themselves to be their very best, may it hurt them ever so slightly.
Well, I got my very simple view on what I would add to make those ability stronger. What do you mean, biased for Rivalry?