Hey,I think radio system would be possible with this way:
1.There would be 2 types of special brick:Transmitter brick and Radio brick.Theres what they do.
Transmitter brick:This is like a music brick,when you hit it with wrench you can choose music,after selected it will start broadcasting it to all radio bricks.
Radio brick:This will play music selected in Transmitter brick like music brick,in set range.It also displays radio chat(see below) in same range.You could be able to select wich ones channel you`re listening,if you have owners trust(if set a trust limit,if not,everyone can listen).
2.Radio chat:The owner of channel can use specified command,like
/radio <text here>
to display a message in his/her channel.
3.Trust system:Owner of channel can set a trust limit,so you have to have full trust/admin/Super admin
to listen.
4.Security:Only admin or super admin may place a transmitter brick.One transmitter brick per person.Max 3 radio bricks per person.
So,what you think?