Also, anyone who thinks the Imperium is more free than the Tau is just wrong. The motto of the Imperium is "Know Your Place". You can't dream of becoming a planetary governor because you aren't a Noble. Too bad. You can't dream of joining the Mechanicus because you didn't get initiated when you were three. Too bad. Nope, the Administratum has no intention of hiring an illiterate bumpkin. I made this same comment earlier, but unless you're lucky enough to live in an area where Imperial control doesn't really extend to, like an Underhive, you have no freedom other than the choice whether to join the Guard. And if not enough people volunteer, they take that choice away from you too. If you're supremely unhappy at whatever you're doing in the Tau Empire, they'll find a new job for you. Because unhappy workers are unproductive workers, and they want you to be productive. In the Imperium, they'll flog you for not working hard enough, then tell you to do your job For the Emperor.
Yeah, honestly, i think the only race in 40k with more individual freedom than the Tau is the Eldar, while the imperium on the other hand lies in stiff competition with the orks here