I like the character so far.
A few points I'd like to make though, Cogs are not known to the general public, so it will be hard for Chie to be obsessed with cogs. There are two ways I can think of to go about this, the first being that Chie is obsessed with space warfare technology in general, starships, carries, strike craft, etc. This can be a useful asset, as she can identify models that are more than a few years old, and know (at least in theory) what their capabilities more-or-less are. After she sees the cogs for the first time, then it's fine if she becomes obsessed with them, and maybe she goes as afar as trying to learn what her teammates' cogs' specialties are. The second option, if you want her to have prior knowledge of the cogs, is for her to be a daughter of one of the scientists working on the cogs. Maybe he breached protocol and brought his daughter to work one day and she became obsessed with them, and maybe he used the fact that she already knows about them to push for them to let her become a pilot or something.
As for games she could play, everyone has a personal identification/smartphone type item called a 'drive'. It's the size of a thumb drive, but projects a hologram to interact with. It detects its holder and accesses their account from the cloud, so stealing it won't give you access to someone else's personal information. It is sometimes used like a keycard to unlock things that the user has been granted access to.
For Chie's history, you can consider several origins for why she is a human living in Horizon. At the beginning of Horizon's history, there was a brief period where Quantums enslaved humans as revenge for their own enslavement, but the Quantums very quickly chose to align themselves with higher ideals and to not repeat the mistakes of their creators. Since then, many refugees from the other nations have fled to Horizon to escape persecution during the Race Wars. If you are making a Wildtype or Ascended character, this is the most likely backstory: that you were descended from former slaves or former refugees. Or perhaps you or your family are recent immigrants. Of course these are just suggestions. Of course, some humans that have been in Horizon long enough have gained positions as politicians and representatives, so if you would prefer a high standing, as like a politician's daughter or something, that's also possible.
Theme song is completely optional
As for you mech, one thing to consider is if you want to focus on beam weapons, mass weapons, or have a mix of both. So far, Askalaphos does most of its damage with a large beam sword, while Farfalla has an even mix of both mass and beam weapons. I'm assuming Rin's cog will have mostly beams. If you go with beams, you would probably have charged beam cannons, where there's a long charge time followed by a massive beam. Mass weapons will basically be large howitzers that fire heavy caliber slugs. The missile option is to launch warheads at the opponent. Maybe the rockets can be outfitted with different warheads depending on the situation.
You could go with one massive primary weapon that is your bread and butter, maybe a held in both hands, and/or you can have a couple of smaller, but still big weapons, maybe shoulder mounted or something.
Here are some videos for inspiration:
https://www.youtube.com/watch?v=mEaFpt7mqV8https://www.youtube.com/watch?v=vfgfxRnVLrYAs for you wishlist, you can either push what your cog is already good at, or cover for what it's not so good at. For example, heavy artillery types usually aren't very fast, if you want to go faster, its a possibility. They're usually not so good at hitting fast moving targets, needing long recharge or reloading times, maybe a hyper mode where things charge faster or something is an option. To become better at what you already do could involve more powerful shots, varied options, versatility, as well as undiscovered science. The sky's the limit for your wishlist. If you can think of it, or provide an example, let me know and I'll try to work it into the universe somehow.
