I can't tell if this is sarcasm or an actual idea you are proposing.

Serious. Fully automated trains have been aroud for 20 years.

Yeah and it's an awful idea to not have any crew on a train. They should be shorter and have people that can be there for emergencies.

To do what that a mechanic one call cannot do?

Be present? Having someone capable to do most basic troubleshooting and mechanic can do being there when it breaks seems quite efficient and much faster response. No travel or alert time. Notify more skilled personnel if found issue not repairable on spot or can't find it.

At the cost of two humans on the train all the time. If that cost isn't greatly higher than the cost of mechanics to go to the train when there is a problem then you have a basic train maintenance issue to solve - or maybe you are running worn out trains that should have been replaced long ago.

> and just works 1 week a month (most of that time doing mandatory training)

This is so out of left field. In what sort of dystopia do we confront the end of scarcity with... more mandatory training? Also, why do you assert 1 week a month? Wouldn't you need four crews to work this section then?

There are a lot of short sections of track that go to something like a grain elevator. They are still worth minimal maintenance to keep operational, but you wouldn't build those tracks today or rebuild if something major happens. They often go more than a month without any trains, then other weeks where they have several. These sections are not worth upgrading to modern switches or computer controls, so you have a trained crew that section, but once the train hits the mainline the crew leaves to go home. Since this crew doesn't get much practice in the real world you need to give them training so that they haven't forgotten how to run a train when the next time comes.