Quoting viech
"The painsaw is cheap but has a very high damage output. It plays a crucial role in taking out alien bases early but can also be used for making dedicated attacks against the Overmind later in the game.
One issue of the painsaw is that while it looks like it would only hurt if if you get into direct contact, it really has a small reach and can damage aliens and structures that are a few feet away. This is important for the handling of the weapon but it's also rather frustrating to inexperienced alien players.
I would like to have the painsaw replaced by something like a blowtorch or thermal lance. It should be a portable device that outputs a thin concentrated line of fire (one that is longer than that of an average real life blowtorch though). The main advantage is that we can keep the current gameplay but make it obvious that the weapon has a small range. The other advantage is that we just introduced the possibility to put alien structures on fire and I want to give this element a bigger role in the game.
The design would be entirely up to your imagination. It can run with any substance you like (gas, oxygen, plasma). It should have the tank attached to it and should not require the wielder to carry parts of it on the body (so that it can also be used together with the battlesuit or jetpack). The design should also differ from the flame thrower which will come in the form of an actual gun (see here for the latest concepts), so I propose you make it look like a military-grade tool that doubles as a weapon since they found out how effective it is against alien structures. At the same time, make it heavy enough so that the player carries it with both hands. That's about the requirements, the rest is up to you!"
Here's some very very basic thumbnails to get started.
cheers