Nanako is funny, sure, but I don't know if she's got enough personality to sustain subsequent reappearances. She's really one-note - she's a baseball fan and she loves black-and-yellow Pokémon, and that's about it. Her Kansai dialect is a nice touch, though, as it helps to remind the audience that we're in a different part of the world now. And I will say that as a stereotype of the average Hanshin Tigers fan, she's pretty darn accurate. That cheer is going to be stuck in my head for a while. ("Furee! Furee! Furee furee furee, Elebuusu~!")
Satoshi comes across as kind of a jerk, doesn't he? He's sparring with a trainer who just started her journey and he uses Lizardon to sweep her entire team? I think they should have expanded on that, and made Satoshi feel a little guilty about stomping a rookie this early in her adventure. Well, he took three baseballs to the face, so I guess that's penance enough.
Takeshi commenting that Nanako would be "a lot of fun" in about eight years or so might just be the perviest thing he's ever said. Shudder...