In the case of voice chat in servers used for gaming, my experience has been that the persistent channels for voice are actually kind of important, it removes any friction from dropping in and out of voice chat, and allows others to easily see 'hey, there is someone in this voice channel, maybe i should join'

But that can be easily faked in client UI. Something like, clicking an empty channel internally hosts a call, hosting/joining the call causes the client to post a hidden "@user is in #call" message, etc.

I did this as a side project awhile ago it was very fun.

https://github.com/adhamsalama/webrtc

I didn't bother adding much styling to the website because I was only interested in the network side of things.