I actually wouldn't be surprised if the Tau got a psyker caste with their rumoured codex this year...
I do have my suspicions that Ethereals are a form of psyker they just hide it VARY VARY well, other wise the things they pull break reality like a Ork and there EVERYTHING lol. All they have to do is say Worm hole opens up, XD and anything with in the Second sphere is pulled through Third sphere is mostly Farsight and Traiter guardsman that joined the greater good. Edit: oops and Orks LOTS of orks. but being kept in check. Edit more: I was just Thinking about ok Tau don't get ther own space travel how would they get there, Eldar are a close ally they could put there casts into Frozen crystalized suspension and the Eldar could transport them safly to the planet, for what trade off maybe resources a safe place to hide in Tau space, I don't know cause I don't know what Eldar really need other then a safe place to do there busyness.
How would Tau fare without the tech to protect them and their ships during their time in that warp jump? There's also the question of reinforcements to replenish their losses in the war, which there will be many. Though at the same time that can be said about the others involved, gameplay liberties are being granted in that sense (way more than 1000 astartes are going to die on Arkhona). Still the others at least have the means to make a connection to their factions out of the system. While Tau would need an accident like you mention to happen repeatedly and uncannily result in the same "accidental" appearance into the Kharon system. This is turning into a headache that I can only blame GW for. Why the hell write a faction into being restricted to their little segment of space in a SCI-FI GALACTIC WAR GAME. Could have still given them the means to just give reason for their slow expansion, birth rates being one I can think of right now. Also don't Tau take in humans? While I imagine they don't have much status in their society couldn't they give insight into warp travel. "Why would they listen to them?" some may say. Well, here's how it would go down. Yes this is totally how it would happen. Totally. <insert individual that would know of the happenings at Arkhona>: "Yo dawg, you hear about all the forces converging on Arkhona? Gotta be something wicked crazy going down there." Tau Officer: "Really? That sounds important. Or just Greater Haters going to war with each other. Again. " <knowing individual>: "Wars always happen for a reason. I heard there's something there. Something that can impact the galaxy!" Tau Officer: "Great scott! We're part of this galaxy. We must get started with Tau shenanigans to develop the means to get there for the Greater Good and stop the Greater Haters!" <Knowing individual>: "Well, it just so happens I have the stuff you need and the know-how. You also got enough humans to make it work. Wanna deal?" Tau officer: "No need! We're crazy advanced and crazy smart Tau. We literally have a pillar of our culture meant for scientific advancements and stuff. Plus like you said, we have humans already." And thus the Tau get their shit together to achieve greater space travel even if only to have the means to rival their enemies who are very willing and eager to destroy their entire existence, planets and all. Fans then rejoice as Tau are then included in more stuff (like not being excluded from EC) and possibly more stuff is added to them. Other faction fans rejoice because they get more reason to unalive them. While GW rejoices since that would generate profit. You're welcome GW and fans. I accept payment in hugs. I thought of Eldar being involved too but the way you say would require them to be allies and not fight each other on Arkhona for if they did then Eldar would simply not grant access to Arkhona, ending Tau efforts right there. Eldar could however orchestrate all sneaky like some means to help them get there (like getting people and tech they'd need to study to them) for whatever prophecy being the reason/Eldar see them as being easier to manipulate once there. To me Tau do seem like the type that would be more willing to ally with "good" factions. Though would Tau trust Eldar at all after the whole Dark Eldar "cultural exchange"? And would Eldar help another "lesser race" to spread to other parts of the galaxy they see as theirs and want to reclaim?
You said something about replenishing numbers ? aren't space marine chapters only 1000 deep? an even if there 100,000 deep that's only a few days of taking losses on the planet in a FPS even space marines don't replenish there ranks by 100,000 a week. Also I only brought up How the Tau get there not how they sustain them selfs but a colony ship could do it, tack on a small mining detachment, and there ability to fight is assured, much like Eldar Tau are not careless with there lives, but if asked they will give it for the greater good with out question. The battles that raged between the IG SM and Tau had them out numbered all the time and yet for some reason the humans lost titans, cruisers, and huge numbers of men before they left, maybe they seen how fast the Tau evolved when attacked and feared that a prolonged war wouldn't be in there favor, maybe the water cast talked the humans out of a continued conflict. Im just coming up with hows and why, with out sitting down and writing out a detailed time line and back ground it with GW approval all I can do is speculate tell I get hard facts, I dis-beleave the pulled into the warp theory and supplement my own.
According to the lore on the Damocles Crusade, had the Tyranids from Hive Fleet Behemoth not show up, the reinforcements sent not get trapped in the warp for a few centuries (appearing latter to save the Tau from Hive Fleet Gorgon) as well as terrible supply lines, the Imperium would have sent even greater numbers and possibly even resort to Exterminatus to clear the way more often (Sept worlds, for example). It was also a fairly small crusade force, as like the Tau, they believed each other to be nothing more than a small empire that would easily be conquered. Apocalypse Warzone: Damocles, with it's ever lovely cover showing Shadowsun a second away from dying, also implies that as the conflict around the Cadian sector begins to slow down, a new, greater crusade would be sent against the Tau.
