Yep they don't need to be busty... Just beautifull. Speaking of Busty Girls... Alpinia was my first 6* and i really like her. She is beautifull, the only thing i don't like is her Bikini...I hope they will make her Bloomed Form similar to your posted Picture.
I also like Kerria... She is beautifull and her Special Attack is elegant... I wouldn't mind if i get her someday^^