The lucky thing is that the Core Book for PTU has got us covered for Pidgey Storm 7.
Swarm Pokémon: Typically, it isn’t recommended to use large numbers of Pokémon in an encounter, for two main reasons. First of all, it slows down combat tremendously to have many more actions per turn, and players can become bored waiting for their turn to act. Second of all, the action economy of many weaker combatants is incredibly dangerous, and you can very easily overestimate what your players can deal with.
Sometimes, however, you have to break a few rules to make an interesting encounter. Sometimes it just plain makes sense that the PCs will be assaulted by a huge swarm of bugs or other small Pokémon. For these cases, you can create a Swarm Template that lets you abstract large numbers of Pokémon into a single entity that roughly emulates how fighting a swarm would work. Note that this still results in a rather nasty encounter! Save it for special occasions. First, decide on how big the swarm is in your encounter. This may vary from merely being a way to group a dozen or so enemies into one to save time and trouble to representing a fight against a flood of Zubat swooping out of a cave to attack the PCs. You can generalize the sizes of swarms into a Swarm Multiplier according to the following chart.
Swarm Multiplier Size of Swarm
1 Less than a dozen Pokémon
2 15-25 Pokémon
3 25-40 Pokémon
4 40-60 Pokémon
5 60+ Pokémon
These numbers may seem high, but, of course, it’s assumed that each individual Pokémon is trivially weak in this case and is only strong due to their numbers. Here are the mechanics for the Swarm Template. The Swarm is treated as one entity and should be given one stat block for a Pokémon of an appropriate Level. It has a number of “Hit Point bars” to its Swarm Multiplier. It can’t suffer Injuries, but as it takes damage in battle and loses all the Hit Points in a bar, its Swarm Multiplier decreases by one each time. The Swarm acts multiple times each turn in battle – it has a number of Swarm Points each turn equal to its Swarm Multiplier that it spends on actions.
The first Standard Action or attack each turn is free for the Swarm. It then subtracts 5 from its Initiative and can act again on that new value. Even if a Swarm hits Initiative 0, it can still act, even acting multiple times in a row on that Initiative tick. However, these actions have a cost according to their Frequency. At-Will actions cost 1 Swarm Point, EOT costs 2, Scene costs 3, and Daily costs 4. Yes, this means an especially large Swarm may use Daily Moves multiple times in a battle, making it especially dangerous. These costs apply only to Standard Actions. For Swift and Free Actions that are limited to Scene or Daily frequency, a Swarm can use each a number of times a Scene equal to its Swarm Multiplier.Otherwise, a Swarm can take At-Will and EOT Swift and Free Actions each time it acts, frequency allowing.
When a Swarm fails to be able to act due to a Status Affliction such as Sleep, it instead loses 1 Swarm Point for that turn. A Swarm always has at least one action each turn, no matter the result of its Save Rolls. Accuracy Rolls to hit the Swarm gain a bonus equal to its Swarm Multiplier, but all single target damage is resisted one step further. Area of effect attacks and attacks that hit multiple targets are treated as one step more super-effective, however.
By these rules... Let's say we have like, 30 Level 5 Battle Pidgeys. An entire box full of this loveable badass.
So. We have 30 Pidgey's at Swarm Size 3 with the following stats:
Pidgey Level 5
HPTotal: 39
HP: 8
Attack: 9
Defense: 4
Special Attack: 4
Special Defense: 4
Speed: 13
As a Swarm, however, they add together to have 117 Total Hit Points, forming Swarm Level 3. In effect, they can take up four attacks per turn. Which isn't bad by any means. So, let's talk damage.
Let's say all 4 actions are spent tackling. Each Tackle averages on 25 Damage. If each of those were a Tackle and assuming they all hit, total damage would be 100. Luckily, each tackle is calculated manually and factors in defense. If you had say... A Squirtle at 17 DEF, then total damage would be reduced to a much more bearable, yet still painful 32 Damage. Rock-Types and Steel-Types however may only be taking the minimum of 4 Damage if their defenses are high enough. Basically a low-defense Pokémon is going to be brutalized against a Swarm, but those that have more defense isn't going to feel it.
---
So, a 30 Pidgey Swarm would be a bit frightening, but I imagine that any well armed group of PCs or NPCs could handle it. The real question is whether your Command is high enough to make that many Pidgeys do what you want. I'd institute Command Checks to control the flock. Kyurin's roflflock would meet it's match against his only average command. He'd manage to get possibly get some of them to what he wants, but eventually his plans would fall apart due to an inability to control the chaotic mass of feathers and assorted bird noises.
He'd probably be better served by raising a single Pidgeot, which are just all around more efficient at flying. However, Pidgey's do have a Power Capability of 1, meaning that they can lift about 2-5 lbs with ease. With 30 of them, that's about 60 to 180 lbs depending on interpretation. Although he cannot control them all, he could potentially use them to fly since he's a rather light character. It might just take a bit to get them all flying in the right direction is all.
---
As for the 6 Pokémon rule, it's for the best. If you compare PTU to something like DnD, you have a lot more moving parts. Each PC can be up to seven different characters in a battle depending on how many Pokémon they have on them.You absolutely must set a limit somewhere. Otherwise, combat situations are going to take a very long period to be resolved. This is also why the Swarm Mechanic is a thing. Because at some point, you do have to wonder just what a flock of Pidgey's would look like.