I thought that by bringing in races that would add legitimacy to the TP,races whose membership of the TP would baffle and give the Federation pause,that could only add to the storytelling potential.
Oh, I agree. What I disagree with is lumping the Gorn into the category of warlike enemy races. That's misunderstanding the whole idea behind "Arena." The Gorn
are (or at least were intended by Keith and Marco to be) the "legitimate" member, the power whose relations with the Federation have historically been mostly positive or at least neutral. No, they're not "pacifistic," but neither are the Klingons or Andorians.
I mean, let's look at the record of prior stories involving the Gorn, in canon and literature (and discounting the Mirror Universe). In approximate chronological order:
"Arena": The Gorn appear to be invading Cestus III, but are ultimately learned to be defending their territory against what they perceive as invaders -- a misunderstanding rather than the result of Gorn aggression.
"The Time Trap": A Gorn is serving on the peaceful Elysian council.
"The Dying of the Light" (Marvel Comics,
Star Trek Unlimited #1): A Federation archaeologist desecrates a Gorn cemetery world. The Gorn respond with belligerence, but Kirk recognizes they've been wronged and makes peace by respecting their sense of honor and tradition. The beginnings of a new understanding are forged.
Dreadnought!: The lower-decks characters who are the focus of the novel include, in a minor role, the first Gorn to graduate from Starfleet Academy.
"Alien Spotlight: Gorn" (IDW Comics): A Gorn crew, seeking to "balance the scales" for Kirk's act of mercy in "Arena," sends a party to rescue a crashed shuttlecraft from the
Reliant. There are misunderstandings that almost lead to conflict, but the mutual good intentions of both sides are eventually established.
Requiem: A militant faction within the Gorn Hegemony seeks to undermine the sitting government and declare war on the Federation, but Picard's negotiations preserve the peace between the UFP and the Hegemony.
DS9, various: Cestus III is now a prosperous Federation world. Despite the fact that the Gorn had a legitimate prior claim, they ceded it to the Federation. Hardly evidence of intractable hostility.
The Gorn Crisis (Wildstorm Comics): A militant faction overthrows the sitting government and launches a war on the Federation, but Picard and Data defeat the militants and reinstate the sitting dynasty, thus restoring peace between the UFP and Hegemony.
Doors Into Chaos: Picard convinces the Gorn to join the task force to deal with the Gateways crisis.
A Time to Heal & seq.: The Gorn are shown to have normal diplomatic relations with the Federation.
Destiny: The Gorn join the Federation's allied force against the Borg.
Now, granted, not all these stories are necessarily in continuity with one another, but there's an undeniable pattern. On the whole, the Gorn have been portrayed as either neutral or guardedly friendly toward the Federation. Any hostility has been either the result of misunderstandings, a justifiable response to provocation, or the act of a militant fringe that opposed the sitting government's nonhostile stance toward the UFP. There is simply no historical precedent in Trek canon or literature for perceiving the Gorn as a "bad guy" race. So I don't understand why anyone would expect the Gorn to default toward warfare with the UFP.