Well, I’m not sure I understand correctly, but this is what I try to do.
On a small map, it is usually possible to create some kind of ring-track. This (double) track connects all cities together.
Then, I just connect every industry I need to this ring, and create side-tracks for freight-stations at the cities.
Now I have only one track which all trains use, passengers and freight.
The challenge in this, is to place all your signals correct to prevent blockings between trains. But this is totally possible! I love to see lot’s of trains using the same tracks, switching tracks a lot, etc.
One downside is, you need to choose your trains carefully. Mostly based on their max. speed. Else the freight trains could end up delaying the passengers trains. But I try to solve some of this now by adding side-tracks here and there.
Also, sometimes a passenger-train suddenly chooses to use a freight-track. Usually, because this route is slightly shorter than the ring-route. Could be solved using way-point so I hope they will be added sometime. Now I usually move the connection-points of this freight track, which normally resolves this.
Hope this gives you ideas