Hate to be a downer like Mist, but I highly disagree with this idea because of several things:
1. As Mist said, this site was never meant to allow people to RP as Pokemon. It's always been about being trainers and catching Pokemon, and it seems like we're too far in now to add something as highly differing as this. Please don't take this as not being open to change, I love sites that grow, change, and develop, I just don't think that this is a change for this site. Oh, and this site is about throwing Mist into all kinds of insane situations, because, well, Wynaut~
2. If we did allow it, there would be several problems I can see happening with it:
•It's all fun and games until someone goes inactive. Let's just say that people go inactive, it's a fact. Usually, you can just move your character along without the person you were with and everything is fine. But, if that person were the main Pokemon on your team, then you're out of luck. Say goodbye to your Pokemon, since you can't very well take over someone else's character. And no, you can't just take over a character while they're away. It's their character that you decided to catch, you have no say in what they do.
•In my own opinion, I believes this opens things up to Godmodding, though I won't rant about the fact.
•The character limit would have to take Pokemon into effect too, this isn't necessarily a downside I see, but something that should be kept in mind.
3. Being a Pokemon really won't change anything about character development. Character development is the growing and changing of a character's ideals and life, and I think it's best done with people, and being a Pokemon won't suddenly make most members spontaneously start developing their characters. No, most will probably stay static, just like most trainers that member creates. If I'm wrong, please explain how a change of species would suddenly allow them to develop more so than they can as a person...
4. If you truely wanted to RP as a Pokemon, you can save a lot of trouble just by doing it as a Pokemon your trainer already possesses and you controlling both minds. Take this thread as an example. I'm writing fro both the perspective of the traine and the perspectives of her Pokemon. If it's done in that sort of fashion, it can easily be done without the bother of all the problems I see with it.