I think STN has a similar setup.
The problem is that the return trains transports the satellite terminal arriving passengers.
Allowing departing to mix with arriving passengers might be a problem.
Have look at MUC.
The train between T2 Main to T2 Satellite has three seperated cars.
First one for security-cleared Schengen departures/arrivals; second one for security-cleared Non-Schengen departures/arrivals; third one for non-cleared non-Schengen arrivals