Agreed on Kwannon, let her be her own woman.
Although I don't want them to be Eurasian Siblings in movie or tv, especially with the swap back. Now that the Asian thing is done, let it be done, and move on from there in TV.
Gemma Chan doesn't have to be a Ninja per say. That in and of itself would be kinda tropey and stereotypical in this day and age. She should just be a badass martial fighter like Black Widow.
Gemma's poise is what would make her a deadly fighter. She'd literally be a Madame Butterfly type fighter, not some brute. More focus on grace and disabling, rather than being a brute.
If she's an Agent, she could be a field Ops style, unlike the comics where she was more a remote viewer type.