Seems to me that a flaming Jack would be terrifying (assuming you have room in your robot/god fearing neo frontals for fear... qed) anyway, if you were a lowly peewee and it came lumbering over to you ON FIRE! It could well cause MOAR DAMAGE (tm). This would enable things like fire walkers to be moar mobile (they are heller hard to path) and Jacks to be Even Hotter (tm). The Jacks already flash when they are burning and the increase in damage would be obvious if it was done by setting the poor terrified com (or whatever) on fire for a short while, damage done as fire damage.
Obviously this applies to all melee units, but most of them would pop if you set them on fire ( I can only think of two, so most is probably an over statement)
