The game engine does load EVERYTHING you are correct.....the only way of lessening the load is to use a specific theatre of operations as pointed out above...this is hard coded I'm afraid.
When I'm testing mods I use what's called a 'Blank Campaign' file which reduces the loading time by approximately 90% but this means there is no 'traffic' in the SH3 world so counterproductive to anyone wishing to play a career
We live with what we've got I suppose
