spoilers:end of spoilers
I think Kantu could have worked too. He's probably in his early 20s by now, T'Challa knew him when he was kid. Just say that after his adventures with T'Challa in Jungle Action he was inspired to serve his country like the Black Panther. Would've been great to see a kid who lived through Killmonger's invasion and the Wakandan crack epidemic (lol) become one of his king's best agents and die protecting the woman he loved.
T'Challa would've felt more personally responsible and it would've been a cool opportunity to do a panel or two in that 70s style to emphasize how far back the pair went. But I agree there was really no way to make the scene pop because T'Challa's supporting cast by and large lacks any personality or deep connections that would make their loss meaningful. So an OC isn't much worse that Kantu or Taku tbh.
And who knows what they end up doing with that female agent lol. Since a big theme of this arc seems to be betrayal (both by T'Challa and those in his life) she could be working for the villain. But unless Ridley wants to play up T'Challa as James Bond I doubt they end up together. But it seems like Storm is out the question too given how she's being positioned as a rival/obstacle to T'Challa's plans. Might be awhile before a new BP LI and I'm ok with that lol.