The republic has snipers, Eoth has sniper like units and long range heroes, Imperials have scouts. I'm not certain if flamethrower infantry fits into current star wars time periods unless it is a droid or bounty hunter. I know there was something about clone troopers using them, but Im unaware if they were still used by stormtroopers after the war ended. Regardless, I don't think they would fit well into the current game because infantry (besides heroes) are fairly weak so by the time flamers get close enough they would be injured or near death.