While perusing around Ex Astris Scientia, I found
this article discussing canon, and my reading eventually reached the following statement in regards to royalties:
If Paramount decided to adopt anything that was not originally created by an employee but by a contractor, they might have to pay royalties for each and every mention of this character or concept! This is the reason why the Kzinti from The Animated Series (TAS: "The Slaver Weapon") never found their way into the live series. The episode was written by Larry Niven, and the Kzinti were taken from one of his novels. It is rumored that the Tzenkethi (DS9: "The Adversary") were initially meant to be the Kzinti.
Interesting. As you know, this sort of problem was why the Kzinti were made into the Mirak for SFC2 (and probably why the Mirak were given canine/wolfman qualities as opposed to feline). However, the Tzenkethi were an oft-mentioned, never seen race from Deep Space Nine, described as adversaries (pun intended) of the Federation in several border conflicts that Sisko fought in (a novel depicting that war is forthcoming). While little more than a passing reference was made to the Tzenkethi, imagine the possibilities of what it would mean if they were meant to be the Mirakzinti.