I seriously spent 10 minutes wondering whether to put this post in Feature Requests or Design. But since there's other weapon suggestions here, I will put this here.
I basically want to suggest a napalm/incendiary round for the GL as a form of area denial. While mucking around release 2.3.1, I noticed walking into or ending your turn near flaming wreakage HURTS (well, my dude was unarmored at the time). And I figured since there's already coding for fire in the game, it wouldn't be that far of a stretch to code in player created flames. To balance it, maybe set a turn limit to how long it persists. I'd say 5-6 rounds is plenty.
The second part might be a little more difficult, burning actors (or character). Allowing flames pass from inanimate tiles/objects to pass ONTO an actor. Basically, walking into a flaming wreakage/napalm and walk back out a flaming torch. Which, if the actor survives long enough, is also passable to other actors. (Imagine a burning armored Ortnok charging your guys)
Now, to justify such a weapon. While I understand PhalanX is primarily a "secret" organization, I would assume it adheres to many unorthodox "as-long-as-it-kills-aliens" combat doctrines. And area denial IS a viable tactical consideration. A damage-over-time effect would be the next best thing since there's no such thing as suppressive fire in UFO:AI (i.e - force enemy combatants to remain in cover with liberal cover fire).