I had the Royal Mail TPO set which collected and deposited mailbags, usually to skid across the lino and deep under the settee, where the cat lurked, preventing recovery!!
I actually stopped an Aunt buying me the Helicopter launching car, as it wasn't "realistic"........Blimey, I was an anorak even then...............
You would not believe the amount of "steam oil" (latterly baby oil) I used once they invented the steam effects unit......... I have recently bought one and am reducing it's dimensions and fitting it into a LMS Princess...in 'N' gauge!!!!!!!
Now for some other possible MSTS "features"...........
A tank car gassing off or leaking (downwards "steam")???
A load smouldering away or fully on fire (damn people throwing cigararette ends off bridges!)
Steam, etc from the breakdown crane while in transit?
Fumes from the Kitchen and Restaurant car roof vents? .....Very overdone sausages, a BR specialty, I remember!
Road Vehicle Exhaust?
Broken down vehicle with steaming bonnet?
Also, I wonder what's ultimately possible using Freightanim in ways not intended............................???
Incidentally, the Hot Box wagon is graphically the same as most of our 7 Plank non-end door wagon output, so can easily be made into other wagons very easily to add variety, just rename the wanted one's main .ace file as per the one in the "Hot Box" set if needed and substitute the .ace file.
Dave