I like the Xindi, too.
I liked the strange nobility represented by the Xindi Council; how these five races seem almost to despise each other (Arboreal/Primate and Reptilian/Insectoid seemed friendly enough at times, but beyond that...) and yet they remain truly committed to the idea of the Xindi as a singular people, as partners in the struggle to survive following the destruction of Xindus. After the homeworld was lost they could have fragmented, but they built the Council instead. And throughout their appearances, there was a sense that they were trying to make it work. They're essentially a five-way racial feud sitting around pretending to be an alliance, and they no doubt have a regularly changing "[...] days without civil war" sign on the Council door, but despite all this they're still in it together. That undercurrent of loyalty was definitely their most striking feature, and did a lot to convince me that they indeed had potential to one day join the Federation. And that when the Xindi-Primate councillor said he thought the Reptilians would return to the Council eventually, he was right.
I think the Arboreals and Aquatics were my favourites; the slower-paced, more contemplative Xindi. Perhaps because the Xindi were introduced as a military threat, and it was a good move to have two of the races seem far removed from the Warrior Race trope; reinforcing the sense that it's a complicated situation, not just "aggressive race attacks".
It's a shame we never learnt very much about Xindi culture(s). From what we did get, the most interesting parts, I think, relate to how the Xindi races view one another. There's a good bit in one of the novelizations where a Primate has a string of racist observations: "The Reptilians thought with their brainstems, the Insectoids didn't think at all, and the Arboreals...they thought, all right, they thought about napping upside-down in trees".
I liked the presentation of a multi-species organization that is always this
close to falling apart but which is nonetheless trying
. They have a genuine sense of loyalty to one another. There's something very moving and noble in that, really, and I'd love a more detailed look at it. And the ability to explore not only five entire alien races (most of them quite non-human) and a sixth, combined culture built by all these different races in tandem would be exciting.
The history of the Xindi is something I'd love to see explored. They're in Enterprise
, and then nothing until they show up in The Sky's the Limit
, seemingly as well behaved members of the Federation (and the Xindi character there was Reptilian, which is even better); there are a few references here and there to Xindi still being a thing in the 24th Century, but no other actual Xindi characters. What happened in between? Did they fall apart, fight among themselves, get back together and rebuild their alliance? What happened to their advanced technology - holograms and vortices, etc? (It's more or less confirmed in the novels that with the loss of the unique properties of the Expanse, the vortices were gone too). How did Earth react when the Xindi popped up again at a later date and offered a hand in friendship (assuming that's how it happened)? How did the Xindi populace react to the revelation that Humans weren't the enemy but the Guardians were?
I still have a lot of questions about Xindi: Why didn't the avians survive, particularly when the Council Chamber on New Xindus suggests that they apparently make it off the homeworld after all? Were the Reptilian warriors all male like Dolim, or were at least half female (these are reptiles after all, you can't tell by looking for mammalian characteristics)? How does an Aquatic "dynasty" work? What does "Xindi" mean
- how did they decide that was their collective name, and seeing as it doesn't sound Aquatic or Insectoid, is it a sign of Primate or Reptilian ethnocenticism (they both seemed quite racist much of the time (the Arboreals less so, but then they were more reserved))?
As for the superweapon question, it's interesting in that Earth, Andoria and Vulcan presumably have detailed information on the creation of a Death Star, and presumably know, in theory, how to blow up planets (not that they'd really need to, since lobbing some antimatter into the atmosphere or ejecting your warp core at the planet should satisfy any "all this needs to not exist anymore" desire you might be experiencing). In the Myriad Universes
story "Places of Exile", Harry Kim reports that a Species 8472 planetkiller (you know the one, I'm sure) is giving off readings similar to that of the Xindi weapon, suggesting that most if not all planet-busters use the same underlying principles to blast a world apart.