While a literal flamethrower would be pretty silly, a plasma stream would hurt... a lot... to put it lightly. I can see a gunboat or cruiser using something like that as a forward gun- perhaps a very short-range (although 100m is pretty insane, perhaps 3-500?) higher DPS weapon with a fairly quick refire rate (let's say 8-12, with a fat projectile) isn't too much to ask. I think. Although, that would first require the option of different types of forward guns- not just the one that the ship was balanced around. That could be where it runs into trouble- especially since it would only really be useful on transports, as getting that close to a smaller ship is practically impossible and getting that close to a larger one is suicide. Hmm.