I do agree with the 911 calls. It is really annoying as dispatcher, when someone type /911 and all officers drive to the crime scene..
As you said. It should only be the dispatcher who see the /911 calls.
But for the radio "block" i don't like it, maybe lower the volume of the others. Else would the dispatcher have a chance to keep spamming the mic, and making everybody else unable to talk, that would be really annoying too.