This Skype use case really interests me a lot, as I have to use it professionally and do not trust this application at all and would like to limit it to a bare minimum: microphone, webcam, screen and one single folder for file exchange.

I never tried Docker, but I wonder, if this requirements can be achieved with SeLinux or AppArmor as they are supported by many distributions and are around longer than Docker?

Would be great to be able to tighten the corset around any non open-source application, to make sure it is not siphoning data.