As mentionend a couple of times in steam discussion forums, i would rather enjoy having the possibility of roaming the entire map of Heavy Haul in a free mode. Meaning you can spawn locos and trailers as you want and then drive around the map as you desire. I know there is a kind of free roam scenario, but i find it rather limited in term of not beeing able to choose what to do and where to go.
Yes driving the AC4400 to shaw mines or Rockwood mine to load coal in service mode would be nice, there is only one scenario for AC4400 coal loading.
I don't know, I'd like more freedom in service mode to take a custom consist onto the mainline in addition to the timetabled ones.