Agree, though I hate to say this, I personally not too keen on Nagisa's voice. IMO, her VA work is actually the weakest of the central cast, but that might just be because I'm not a fan of her voice line.
Anyway, I do hope there is a 2nd series, and Takamina (real live) would join the cast with her recently comments that she would also like to try out some VA work herself and actually tried out a line from Heartcatch Precure in one of her regular shows that is hosted by Kinki Kids and had Mizuki Nana as guest. Her voice range is actually pretty impressive being one of pure singers of the 48 group. Not to mention she did beat out fellow Team Dragon members [Aachan, Yuko, Kojiharu, Tomochin, Yukirin, and Mayuyu) to get a cameo role in Episode 71 of Dragon Ball Kai.