i used for a lot time skype classic while i had a very bad pc for gaming with my friends, it was perfect when skype was not responding(or frozen) you was able to still hearing and talking with your friends on calls, also classic skype had that feature of
calling 200 or more people on one group
Share sound and image (individually)
so if there was a custom server for classic skype connection
The “still talking to friends even though it’s not responding” ‘feature’ is also present in Messenger, most media players and many other applications too. This happens because Windows determines the “not responding” state based on the user interface thread of the program only, whereas the audio processing is run on a separate background thread at high priority, and remains running until you fully end the program.
Creating a “Skype server” would be extremely challenging for lots of reasons but perhaps someone will invest the (likely years) of work to do it someday. Maybe even you? 
lol discussion of software that killed messenger 