a thermobaric weapon isn't designed to set things on fire, it's designed as a pressure wave explosive device. I agree with Plasmarobo here, tar already accomlishes what is described.
the "thermo" part suggests heat is not an unwanted side effect and I already mentioned my logic for not insisting on having a blast AoE , think of my using it as a means to get the discussion off the keyword "tar" which apparently triggers unpleasant memories.

The tool "tar", which has nothing to do with the weapon I'm fantasising about, requires that you fly close enough to a ship so that it cannot avoid your cloud, and can be tricky to use on a ship that doesn't have centerline guns like the junker. It is also the antithesis of "remote", it is literally "in your face".
I think it's worth noting that the mines currently in the game have a good chance to ignite a 5 stack of fire on everything in its AoE. Do we really need a second mine that's only good at setting fires?
You have a chance to ignite stuff with incendiary ammo, and you have a flamer. Yes I want to drop flaming booby traps around the map.