Does anyone remember Picard's reference to a bad first contact at Station Salem-One that lead to interstellar war? For the longest time I wondered if that wasn't first contact with the
Klingons and wonder if that could happen in maybe like the series finale here to lead us into the Trek we know. That would mean
no Klingons in this series.
(EDIT: Now that we have the Battle of the Binary Stars in DSC as the start of Klingon war, maybe Salem-One is the start of the Romulan one.)
Maybe no
Romulans either. That is, neither the the characters nor
we ever see them. It would be cool if we could experience them as the characters did, just combat and dread and paranoia. When they do show up in a chronological rewatching of ENT and TOS, "Balance of Terror" should be a great reveal/rewatch.
None of the races that show up later (
Gorn, Borg, Ferengi) or that you imagine were only contacted with the expansion of the Federation down the line (
Cardassians, Tzenkethi, Talarians, Miradorn). Also, no
Yridians, as they were thought to be extinct until Captain Ransom made first contact with them in the 24th Century, per VOY's "Equinox." Maybe we see an early unofficial “first contact“ with one of these aliens over the course of the series, if only as a lone individual far from home due to whatever sad story that lead them there (e.g. that Cardassian in exile on Vulcan that Dax met during the TOS era that she mentioned in “Trials and Tribble-ations”).
A definite yes to the
Orions. They're the remnants of a vast ancient empire and could be utilized in multiple ways. The
Kzinti could showcase contemporary makeup and CG techs. Maybe this is the series to blow up the
Tholians too. The
Malurians were used interestingly in ENT, and they could be troublesome baddies in this century before Nomad blows up their homeworld in TOS. The
Tarellians from TNG were still around at this point and could also be updated and reworked as baddies. The old Romulan saying about "never turning your back on a
Breen" makes me wonder if they aren't ancient adversaries not too far apart...maybe it's because they turned their back on the opportunistic Breen that they lost the Earth war to the upstart humans.
Speaking of, the
humans could (and other good-guy factions) could have different forces within their governments or populations that cause trouble. Maybe there are specters of Earth's past ready to take the reigns again should the good guys falter, or a coup on Andor, or a civil war on Tellar, etc...
Also, there's a lot of other yeses to see and update and expand upon:
Andorians, Tellarites, Ithenites, Coridians, (also from TOS's "Journey to Babel": those tall guys, the purple women, the silver-haired people),
Tiburonians, Argelians, Medusans, Ardanans, Rigelians (including the giant ones from TOS's "The Cage," and the Vulcanoid and Chelon variety. I'm so-so on the ENT ones as they weren't visually interesting enough to warrant their further complicating addition),
Antarans, Saurians, Caitians, Aurellians, Nasat, Edosians, Deltans, Aaamazzarites, Arcturians, Megarites, Rhaandarites, Arkenites, Arcadians, Bzzt Khat, Xellatians, Pandrilites, Ariolos, Monchezkins, Roylans, Denobulans, Sulibans, Nausicaans, Alpha Centaurians (retro little green men with antennae? "Grey" aliens like from X-Files/Babylon 5? Preserver-planted ancient Greeks as in
Worlds of the Federation? A non-humanoid fifth founding-world of the Federation, to be more realistic and showcase special effects tech?), among others...