Hi there! This seems like an amazing premise, and I would love to jump in with this.
Awesome! :D
But first, question. In the Pokemon Mechanics, it says that stats have no real bearing in combat. Does that mean that Stat boosting moves (Swords Dance, Nasty Plot, etc.) and stat debuff moves (Baby-doll eyes, Screech, etc.) are completely useless in combat?
Stat boosting moves will improve the Pokemon's physical/mental state to make them more effective in battle. Hone Claws literally sharpens their claws (raising Atk.) and perhaps makes them focus (raising Acc.). Baby-Doll Eyes can demean the opponent, making them not want to attack with as much strength against that who performed the maneuver. They still boost and debuff, but there will need to be a reason why, a cause and effect, that should be described when performed.
Also, in the same area, it is said that Pokemon can only use moves of their type. Does that mean I can't have a Hyper Beam Butterfree? (Butterfree is Bug/Flying, Hyper Beam is a normal type move. No type relation)
Moves must align with the Pokemon’s type and species...
You must be able to argue that a Butterfree can perform a beam of pure energy.
But
most Normal-type moves are
relatively universal to all Pokemon.
Also, the use of Dark-type moves by Fighting or Ghost-types
can occur.
The use of Psychic-type moves by Ghost-types
can occur (and vice-versa).
Ground-types
can learn Rock-type moves (and vice-versa).
But they might not. It's up to you and of what the Pokemon is capable. It's also up to logic dictating that a certain maneuver performed by a certain Pokemon is possible given it's natural typing
and the species of a Pokemon (Drapion could learn Pin-missle, Bisharp could learn X-Scissor, etc.)
I hope that clarified enough. ^^