I've really never been a fan of RHW's idea of the Tzenkethi that would have appeared in The Adversary. Heavily armored lizard things with big arms? Sound to me like a Gorn knock-off, and the Gorn (until recently in TrekLit) haven't gotten a whole lotta respect. Why not just use the Gorn if that's what you're looking for from the Tzenkethi?
Actually Robert was thinking of the Hakazit from Jack Chalker's
Well of Souls universe. And given the
T. rex analogy, they sound more like larger versions of Dr. Ree from
Titan than like the Gorn (though the "In a Mirror, Darkly" version of the Gorn is a bit more dinosaurlike in body structure than the "Arena" version).
Though I do agree that, given the inclusion of the Gorn in the Typhon Pact, it would be preferable to make the Tzenkethi a little more distinct. Had it been up to me, I would've used Robert's idea as inspiration but maybe played up the "heavily armored" aspect, giving them kind of an insectoid chitin plating over a raptorlike body plan, or something along those lines.
I'd prefer the cat-people approach because at least it'd be something not so close to the Gorn. And except for one Animated Series episode and one early TNG episode, I can't think of any cat-people from Star Trek.
The Caitian Lt. M'Ress was in six TAS episodes. There were felinoid aliens (generally assumed to be Caitians) in the Federation Council scenes in
The Voyage Home. There was a three-breasted felinoid alien in
The Final Frontier. In the literature, we've had the Eeiauoans and Sivaoans from
Uhura's Song, the Sadrao from
The Wounded Sky, Snnanagfashtalli's species from
The Entropy Effect, the M'Dok (renamed from Kzinti) in
The Captains' Honor, and no doubt others. Not to mention the Grond in the DC Trek comics. Felinoid aliens are a huge cliche by this point, in Trek and elsewhere.