[KMFrog]

trying to replace sounds is a bit "old school" now with the implementation of pure-mode. Most decent servers will filter out your modifications...

Playing sounds to clients is easy enough, creating fake radio messages should be possible (im not sure how you would get the player map location in the message) the only problem i can see if blocking the existing radio messages like i said.

if i get a chance this weekend i may be able to cook some code up for you to at least get you half way there