A silly question: How do I program a flamethrower unit to use the effects that go with the flamethrower rather than the paratroopers? I know it's possible but I can't seem to find anyone who's done it successfully in a mod so far.

I have no idea. You did already ask in the creation and customization forum, possibly the unit requests thread, or the thread with the flamethrower art, right?

Moved to the Creation & Customization forum.