[morfangdakka]

Me personally I would use some Militarum Tempestus Scions squads with some added fire warrior bits to them to show they willingly joined the tau. I think painted the same scheme as tau they would blend right in with them. Skitarii Vanguard and rangers could be another option for some. Or you could always do cadians or Vastorian first born with some pulse rifles and tau bits.