I second that. And if it could be vertical as well. Also let us choose what elements we can see. I would prefer not to see any info on signals.
I think a more useful version of this would be to have trains exporting some sort of telemetry data that a separate app can interpret and display information for. This would need to be set up for each train, but it would be very impressive if there was a Zusi-style second display that could show a TMS screen, the dials, or something else. The app DashPanel seems to work like this. When I play Euro Truck Simulator I can have my speedometer on a separate display or even on my phone. To be honest I don't think DTG need to do any work to get this added. Some of my AP content has created CSV files with some sort of data in them. I don't know what the data is or what the files are used for, but if a train has the ability to write to a file it could be a good sign. That said, it could also be used maliciously, so DTG probably would want to fix that before something bad happens.
Look at CobraOne's Raildriver adaptor software, this collects all the telemetry from the game and uses it to enhance the raildriver, it can be displayed on another screen as well, or piped into another application.