alright, because DC has so little to work with with Vixen and African heroes it was a little harder creating this list. so my angle for the Vixen family's niche is two fold; their reason for being and their brand aesthetic. So in the New 52 Batwing title they introduced a team called
The Kingdom, who were the first superhero team to come out of Africa; think of them as Africa's Justice Society of America.
The Kingdom eventually fell (read the run, it's pretty cool) and is currently still defunct. I would have Vixen work for the AU (African Union) and spearhead the a revitalized iteration of The Kingdom as a panafrican superhero institution that's mission is to dismantle the lingering legacy of colonialism, african exploration, and attempts at neo-colonialism. now I'll admit, it's a lofty concept to tackle. it's a hard sell but, speaking from my own experience as an african person who grew up in a relatively political household in regards to african cultural issues, I feel this would be the most compelling and genuine motivation to explore for an African superhero or an "African Justice League", since we rarely see it (sans Black Panther from time to time obviously). So that would be their reason to assemble under Vixen, she's the Superman that they all rally around, The Queen. as for their aesthetic niche (maybe thematic connection would be better wording? meh I like aesthetic), I would have the Vixen family focus on heroes who use the occult and mythology, specifically animals themed and natural life-giving elements to compliment Vixen's connection and mastery of The Red.
Vixen - head of the family, Queen of the Red and Queen of The Kingdom
Kuasa - I did like the idea of Vixen having a sister, the addition of her and Mari's grandmother were probably the most interesting thing Legends of Tomorrow did with Vixen. I wouldn't want her to be jealous of Mari or a villain or an antihero, just a team of two sisters fighting crime. I don't know what her ability will be, maybe she takes one of the names of the OG Kingdom mantles like Diety or Dawnfire. they could keep her closer to her Legends character and have her be an avatar for Oshimiri (aka Mamiwota) because it has the potential to touch on how African stories are told; if you know the history of mamiwota you know what I'm talking about. Think of her as their Aquaman or Mera.
Benjamin Turner (Bronze Tiger) - I know people who grew up on JLU love Vixen with John Stewart but I'm a firm believer that Bronze Tiger is her true love. I would like to use Ben as our dispora avatar who we can watch gradually acclimate to African culture. plus, if we really wanna get wild with it, I like the idea of him having a solo story of some kind where he's rediscovering and refining African martial arts to push his limits as a martial artist and becoming like an African Iron Fist via some kind of african esotericism. While I'm tempted to change his name to make him feel more afrocentric, I find it funny and kinda fitting that there are no tigers in Africa and the dude from the diaspora is named "Bronze Tiger", and that would push the character too far from himself for my liking.
David Zavimbe - I would have him be the Batman of the group, he's Vixen's first recruit, and the right-hand in the field. He currently doesn't have a hero identity, he only retired Batwing because he wanted to be his own symbol of justice not Bruce's, so we know he's out there doing his thing and he's a blank slate to work with. so my proposal? ANANSI FROM STATIC SHOCK BABY! (I will always pitch Anansi no matter what until DC makes my dreams come true!) anyway, anansi pipedream aside, I love David Zavimbe and I see him as the human element, no superhuman martial arts skills, no superpowers, no magical abilities, just grit, whatever gadgets or magic items he can get, and the human spirit. also, I want him to have Lord Battle be his benefactor because DC inadvertently made Biafra an afrofuturistic reality and in my mind Lord Battle is an igbo man
and I love that
Freedom Beast - I know I'm alone on this but I always read the post-Flashpoint Freedom Beast as a young hero, like the anime young head of the company prodigy trope. I like the idea of Vixen being his mentor training the next generation Red avatars. he was Bwana Beast's sidekick/protege, so I see nothing wrong with having him be Vixen's. if done correctly, it both strengthens Vixen position as a hero by giving her a young hero to stick on the mini league teams (like Young Justice or Teen Titans or Titans) and it gives Freedom Beast an excuse and a place to pop up more.
Bloodwynd - Necromancer = King of the Dead anyone? I love Bloodwynd and the idea of a black superhero who draws his power from his ancesteral heritage and his history; especially because of the long lasting legacy of colonial iconoclasm is Africa. think it would be a fun twist to have Bloodwynd be a Liberian superhero, who's family dedescended from one of the early african american colonials and the natives, and the blood gem came about from his indigenous side's rage from colonialism.
Doctor Mist - Doctor Mist is one of the most interesting African heroes because he has such an interesting set up but we know nothing about him. I would love for the Lost Kingdom of Kor to be fleshed out, I think someone once pitched that he could be the one who created various magical items throughout the DC universe including Vixen's totem, I would go with that (and have him create the spider totem too). He can be the Doctor Strange of their team and Vixen's mentor in fulfilling her destiny as the wearer of the Zambezi totem.
Cheetah Amazon tribe - This one is the one that prompted me to do the Vixen family. So in Wonder Woman we learn that the tribe of women in Bwunda who were believed to worship Urzkartaga where actually a tribe dedicated to protecting the world from here. this reminds me of the Leopard Men of West Africa, a secret society that's traditionally a male only, and I think it would be cool to expand that tribe's mythology (naming them) and introduce a champion for them to team up with Vixen and sorta "marry" that tribe into the Vixen brand's mythology. if handled correctly, this could be Vixen's connection to the Wonder Woman mythos.
adjacent characters:
Beast Boy & "Old Man" Animal Man - I think Vixen doesn't need to absorb Animal Man or Beast Boy into her brand but I would want all the Guardians of the Red to be in regular contact with one another. much like Vixen is training Freedom Beast, I like to see a retired Animal Man mentoring Beast Boy in the ways of the Red and see Mari and Buddy kinda seeking advice from each other.
The Spider God (aka Compe Anansi aka Odudo Okwanka) - I would want the Spider God to be a Red Entity (a being born from and an embodiment of The Red) to be a guiding force in Vixen's corner but he's slso a trickster so he may appear to be evil in some stories to teach her important lessons
Justice League Dark/Sentinels of Magic - I think Vixen should be a staple of at least one of the magical teams at DC. simple as that
villains:
Urzkartaga - an evil force of nature
Red Lion (I would roll Lady Marabunta in his inner circle) - African Dr. Doom, that's it.
Cheetah - I would like for Cheetah (in the context of a Vixen story) to represent the appropriation and bastardization of African
Jezebel Jet - I like her as a dark mirror to Vixen, and a commentary on corrupt african capitalist who will sell their own people up the river to profit for themselves.
Prometheus - Prometheus is a man who actively seeks to do evil and crime, I think he's perfect to be the foil to Vixen as the face of Western/Eurpean imperialism on the continent of Africa and all the crime it entails.
not my best list, maybe I'm too close to this one and wanted to do too much but that's what I got.