Sadly as far as I know changing animations (other than attempting to assign a pre-existing one for the unit) is currently beyond the skill sets of most of the modding community. At the moment I don't know of anyone that has a way to extract the game's animations so that they can be altered, so twould mean creating a new one from scratch. Also when you request a mod please give as much detail as possible. I know nothing about Tau/Fire Warriors, so even if I could do the animation work I would not know what you want for it.