Imho there should be some option to automatically fill in your nickname if you wish. So if I'm on our gang channel then I press the enter the radio will not start with empty message, but it will start with "Sius: " and then I'll type my message. So:
Press enter => "Sius: " => "Sius: Good news everyone!"
If one wants to act like someone else then he will simply have to change his "auto-fill-inl msg" from his nick to someone else's or leave it blank.