how about putting one of these on a train car, for protection over long distances, or instant firepower on the train lines?

That is actually a really good idea. I'll definitely consider adding that.

Do it! I hit the ceiling with my adaptation of your mod on trains, maybe you can do better? :)

I have an idea how to do it, but I cannot do graphics, and I would need a small train wagon looking like a sort of drone controller. So I gave up on the idea because I don't know how I would get over that problem

Yeah I see, I was thinking too about drone-wagon. And it will fix all problems dedicated to render layers and sprites overlapping.

But, you can try to play with artillery turret, you can replace graphic and cannon projectile with tank, car and flamethrower. But there is another side. It will need a script that will target enemies automatically. And maybe use separate marker from artillery. But it is looking this way far more better and fancy

I was thinking about using code from AI vehicles and just put a turret of a car on top of wagon that way it will fire automatically. But not sure 100%