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Ion was largely depicted as a girl who would've been helpless without her friends for most of the time in Ar nosurge. Granted, I haven't read the full summary of Ciel Nosurge (though I had read the short summary of it and Aquagon's counter argument when somebody accuses her as a straw idealist), so she might've done a lot more back then.
Her first song in Ar nosurge has a significant impact to the plot (establishing the Earthes channel, restores her memory, but caused massive Sharl propogration and caused serious trouble for Felion and Delta's party) and was forced on her in her catatonic stage. XIO_PROCEED puts her relationship with Earthes as the defining trait. Lxa ti cia was a song that Horus gave her to train Kanon and Cosal, making her something of a stairway to the endgame. And lastly, she was nearly absorbed by Maternal Overseer when she tried to sing EXPAJA and Ra Ciel Reincarnation, both times, she needed her friends to bail her out of it.
As for her Genometrics, she is REALLY dorodere, especially at Renall and Nay's 2nd stage. Then again, what would you expect from a girl of extradimensional origin and a robotic and speechless avatar with no way to communicating with her apart from VN-esque choices. And as Nelico said, she's not really the "liar" type of dorodere like Luca, and her first Genometrics is in fact the exact opposite of Luca's, as she made the Quality Control stage (which is an unusually strong mental wall on its own) out of fear of a relationship built on lies.
As for her ambition, now that's the one thing I admire about her. She sure dream big for a girl from a rural town, and she even resolved her parent's disapproval and managed to overcome the swimming test on her own merits. Granted, neither of those would be possible without the newlywed couples and Yumekichi, but she certainly has a strong will on for her ambition. I'd say the game would be more interesting if the plot emphasis that part of her a bit more, though I'm a bit vary of her being a clone of Yuuki Asuna. Her incredible song of miracle aside, she also made Yumekichi, the Ciel Nosurge terminal and link it to Earthes by herself, and all of them have changed her life for the better, so it's not much of a wonder why she could trust Earthes as much as she did (superficial, yes, but I doubt anyone else could trust him more than she did).
She could even learn to love someone on the other side of the terminal, despite being unable to see or hear from that person if you date her long enough (in Ciel nosurge) or Dived deep enough into her (in Ar nosurge). I've tried to claim myself as a completionist after clearing last level of her Genometrics, fully expected to get kicked out. but she accepted that (to my surprise), She sure goes a long way when it comes to trusting someone who were able to Dive that deeply into her.
Now, I'm not saying it's wrong. Considering her backstory of Diving into Ra Ciela knowing she won't return ever again to escape getting killed and getting imprisoned there for years she REALLY need her friends to support herself. Her characterization is all right as she is, but a lot of her character development is largely reserved to Ciel Nosurge, so it's not surprising that she was accused as brainless or straw idealist out there. Her path seems to compromise a bit much to emphasize her relationship with her friends and Earthes. Things would've been better if the Oversight powers and their way back are explored a bit more instead of just a deus ex machina from Ayatane and Prim.