Adding a fictional track that magically removes trains from existence and/or somehow transports them on a fictional route in order to stop them running on real tracks where they'd obstruct other trains completely goes against the entire premise of SimRail altogether, it's a terrible solution for a multitude of reasons, and I don't even know where to start.
I'm with jeroezie here:
Separating the traffic would make the entire track boring for both the dispatchers and the drivers, and it's important to keep in mind that passenger and freight trains can coexist, which they do, on real tracks, in real life.
I also agree with Mywasher:
In that time-window separation is, after carefully considering the vast inferiority of the other options, like:
-The removal of freight trains from CMK altogether, which would make dispatching, like Mywasher said, as boring as watching paint dry
-The creation of a fictional alternative route, which is about the most unrealistic solution I can even think of, short of adding jet-assisted takeoff thrusters to all freight locomotives,
and
-Accepting the current state of having a weird sort of "Pendolino lottery" in which you get delays, annoyed drivers and complaints, sometimes for no apparent reason,
the correct (read: "least awful") way to deal with this issue.
As a personal note, I prefer dispatching over driving, and while I do agree that mixed traffic is more fun to dispatch, I can't help but notice that having to deal with the chaos it inevitably causes does take some of the fun out of being a dispatcher, especially at the more busy posts, and especially especially when it stems from upstream damage done by AI, over which I have no control, just like the AI seemingly doesn't have control over anything at all. It's not uncommon for the AI to ask me if I can accept a high-priority train on the opposite track because the freight train that it sent out just a few minutes earlier is still blocking the track that goes in the correct direction and, perhaps more importantly, wouldn't have slowed the higher-priority train down even more than it just was by this completely unnecessary kerfuffle.