Perfect idol? To me, that's an intangible quality, it has to be someone who reeks of 'idol!' Of course, singing, dancing, beauty and character play a large part and the perfect idol would excel in all of those. So, IMHO, H!P's perfect idol, the one who screams "THIS IS AN IDOL!" is Miyabi Natsuyaki. Particularly impressive and endearing about her is her fan service, I've never heard an ill word about her manner with the fans.
Now, if the question was "who in H!P typifies a perfect woman" I'd have to go with Maimi Yajima, the girl whose feathers cannot be ruffled and who has absolutely no weak points in womanly charms.