Optimization is talked a lot about here, but what about using memory more aggressively for those of us that have large amounts of memory available (32 GB, 64GB, or more) ? DDR4 has made it very affordable to have such capacities ( I have 4x16GB) on recently built computers. Sins of a Solar Empire is a game that used an interesting technique. It loaded all of its assets into memory once at the start and had near instant loading screens as a result. Something similar might work well for TSW, Train Simulator of old certainly had a very noticeable hiccup on loading particularly detailed cells.