Well I did some digging around and using my computer skills, I found in the client's root files there is no plugin support. The only way I can find to get a plugin working is to have it already installed AND ACTIVATED before the 3.1 update (however this only works for some plugins - unfortunately not the WWII Radio).
I will try keep this updated as I look around but there is no evidence on the TeamSpeak website that versions 3.0.8.16 and above have a solid plugin base. Also, the radio plugin itself is only updated to version 3.0.1.1, which is compatible for TS3 version 3.0.8.15 and below. It isn't going to be my first priority but there is an old radio plugin used for the VATSIM server that I have installed on my PC. Generally it is for FSX but, I can have a go at changing its root files for TS3, and give it a go. I won't promise this however - I don't know how its going to turn out.
I'll try to keep you posted on the upcoming events and remember... If my PC breaks because of this it's all YOUR FAULT!

Have a good one,
Mikey