I think train sim world should include all the details to make the game so much more immersive. That's why I think GSM-R should be useable and to the full extent. I know some trains also include partially working GSM-R's but I think you should be able to type you own headcode and setup it manually rather than just turning it on.
The problem is, not many routes have an end station, so the GSM-R would need to be set up already for those particular services. Services at an end station I agree you should be able to set up yourself.
Yep, the dispatcher doesn’t need to be advanced or changed for this to be a feature, it’s sound simple and should be easily implemented.