Also, I'm thinking forget Niven history, create a new one. Maybe call them the Mirak.
Well, then, why not just create a separate felinoid warrior race? It's not like the Kzinti are the only such species in SF by a long shot
. So if you're going to separate them from their Nivenian elements, they're not Kzinti at all, just Felinoid Warrior Alien Race #47.