I could actually think of a game based on Ciri that might be enjoyable. But that game would be completely detached from Witcher 3 and anything that happened there, Ciri included (character + powers). It would be based on Sapkowski's (non-canon) "Something ends, something begins" short story depicting an older Ciri after the events of the saga:
Geralt raised his head, yanked out of his slumber by ....
Interesting, thank you for linking it.
I wasn't yet convinced to read the new book, being announced as non-canon and only partially related to the Witcher universe.
But it might well be a source of viewpoints where Sapkowski wanted to go with the characters.
I have to pay you tribute for wanting games with such twisted and broken characters. I'm pretty sure that good devs shouldn't give the fanbase exactly what they desire. Few would ask for hard choices, unexpected loss of beloved characters or chooices between two bad options. Yet that's what makes a good story.
But there is one special thing about her being protagonist we haven't really considered yet.
If we play as Ciri, we would shape her. If done right, she would be the person you would like to see in your game, and the person I'd like her to be in my game.
There's quite a spectrum for Geralt to be either jerk or hero in the existing games, yet the devs are still relatively limited because he is described in detail in the books. Ciri is, too, but she is merely 17 by the end of the book canon. Geralt is mature and settled from the very first book, his special morale has developed over a century.
We know from the books that Geralt doesn't like theft, even if it's for survival (like when he travelled with Zoltan's boys, before meeeting Regis). It's however not firmly established for Ciri yet. Sure, W3 paints her as idealistic mostly, but not in such detail that there isn't room for some of the stuff you posted. Most of her positive behaviour is directed towards people who are obviously her "allies", we know little about how she would treat people she's on mostly neutral terms with.
Think of Commander Shepard in Mass Effect. While you obviously can't choose to make him Satan himself, you can form him/her to be quite a varied, even borderline evil character. Or you can turn him/her into a "Mary Sue", if you want. I believe the term loses his meaning in an interactive medium like a game.