The list is still on the works but most Legendaries will have attributes that go from limit 10 to 20. They'll be hard to beat and incredibly powerful, but still defeatable with a good party. As for HP, you can compare the Videogame base stats to the point limits on the book's pokedex entry and see the pattern, 99% of all pokemon attributes are based on their videogame stats, so it shouldn't be hard to do what you want.
Well, this is what I could manage so far: [Google Spreadsheet](https://docs.google.com/spreadsheets/d/1-v6Oqu91hp63qYlsoQoKiN70b5pCnPPK5Ysc91TCPGM/edit?usp=sharing) I took the values from Bulbapedia and divided them by 15. The result looks okay-ish but there are some oddities, like some starters having 4 HP and Diglett just having 1 HP. I need to come up with a better formula later.
That's not the method we followed but you got pretty much the same results in most cases. What we did after we decided to use size as the base instead of the HP Stat from the game was that no First-Stage Pokemon could have less than 3 Base HP, Second forms and non-evolving Pokemon couldn't have less than 4 BHP and Final Forms couldn't have less than 5 BHP. Mostly due to balance and to mantain the feeling of progression upon evolving. I would honestly recommend you to use the BHP attributes on the book instead, if you wish a Pokemon to have more or Less HP you can use the "Overgrown Pokémon" Formula to increase or decrease Base HP to something more fitting to your tastes.
I'll include the evolution stage advice to a finer combing of it. I noticed some 2nd stage Pokemon had pretty low HP, such as Kadabra. But as you may have received from my message feedback, I think the size-based approach is prejudicial to pokémon whose high HP is part of the appeal and strategy, such as Blissey and Wobbuffet, and it seems to lead to really strange results when applied to snake-like pokémon. Arbok has more HP than Snorlax, Dragonair has more HP than Dragonite. At the very least it needs some finer-tuning and some balancing on pokémon that are much longer than they are wide. But honestly, I would rather stay with a game-based list. I'm used to squishy large pokémon since back Red and Blue and the first season of the anime, where Onix was one of the first challenges ever. The setting has many cutesy unassuming Pokémon which are pretty powerful, regardless of their looks and size. I just want a system that enables me to reproduce the world of Pokémon.
Well, as we always say, Don't limit yourself. In the end you know what is fun for you and what is not, rules can be changed to better suit your tastes, the list you have already is pretty much what we would have if we hadn't made any changes. If you test it and you find it fun we could always use some more feedback about how it worked for you.
As a Pokémon fan, I've enjoyed countless hours of gaming since Red and Blue, however let's not assume videogame mechanics are perfect. HP has been something odd since day one, and there doesn't seem to be much logic behind it, it is kind of maybe used sometimes for some bulky or fat pokémon, but not really. It is simply inconsistent. It is just a number to add some general resilience. And that's not wrong at all, I mean, that's how things usually work in videogames. Nonetheless with Tabletop RPGs, even though the setting is all fantasy, it has to be plausible. That's where HP needs something to back it up, something meaningful, something that can be seen and measured just as you would measure someone's Strength by looking at its muscles, or Vitality by looking at the fitness of the body, something real enough to go along with the flow. I understand what you think, Twilight Vulpine, however, from what I'm seeing, your worry is more about a couple of specific Pokémon, rather than the HP system. You tried to get similar numbers with your formula to match the corebook, so I believe you're probably much better just homebrewing those six or eight or ten Pokémon that are making you uncomfortable. Also it will be so much easier for you if you're planning to GM.
If you were to go along those lines, you'd have to apply the same to everything else. This is a setting where creatures generate fire and lightning, eat dreams, even materialize rocks or explode and be fine later. How do you even justify Special's energy generation? Pokémon are fantastical creatures that don't follow an obvious logic. So much so that researchers dedicated to understanding their unique capabilities were present from day one, and a scanner/encyclopedia is a vital tool for trainers. More than that, you need to keep in mind that the people that are going to play this, are most likely people who either played the games or watched the anime. They will have some idea about how deceitful looks can be. After all, who does not know Pikachu, the tiny powerhouse who beat things far larger than itself on a regular basis? For some, part of the appeal comes from having these cute things as battle-capable as huge ferocious beasts. Look at the list of the top 10 highest HPs in game http://www.serebii.net/pokedex-xy/stat/hp.shtml Half of them don't look tough, big or a t all imposing. The setting never meant for HP to be about how big or rugged they look. It's far more "pulpy" than it is "gritty", so to speak. Your approach might be more "realistic" in a way, but it takes away from the fantastic and diverse feeling of it. It also takes away from the individual pokémon dynamics. Regardless of their size, some are meant to be squishy, some are meant to be resilient. As far as GMing goes it does not help my life when I'll have to handle expectations and usage based on these differences. Those snake pokemon are not balanced compared to the rest of them. They might expect an easy time against an Ekans but it's far more resilient than they would expect. It does not even look that tough, it's just long. Then there is Wailmer that can be a game-breaker from being mildy resilient to the single heathiest thing in the game, one order of magnitude above the average. Even among starters Serperior having more HP than Torterra does not seem right, neither in a game-based manner nor in a "realistic" manner. Serperior is a leafy snake, Torterra has a giant rocky shell. Tyranitar is the literal "armor pokémon" and it has less HP, and not any more Vitality. There are too many weird things to just change one or another. In changing the system to use a size-based HP, the identity and relations between many pokémon was lost. Even if that's what you want for your system to be like, well, it's your system. But I'll still go and either find or create game-based alternatives, because I am absolutely certain that would suit my group and campaign better.
I'm sure the system will still work with your homebrew : ) Hope you have fun.