Thing about sectors is that this game is that every sector loaded in memory uses one thread for sector updates, regardless of if its SP or MP or even dedicated servers. Going about how you want to keep sectors loaded, you would quickly run out of threads on your CPU and start getting terrible framerates or even crashes.
Instead, I recommend a mod, which is on this forum, that instead of keeping sectors loaded, it records the last time you were in a sector, then when you come back, it calculates game ticks to progress production on sector reload. Its called Out of Sector Production.