On Windows, we have a very handy feature in WASAPI mode called Maximize Device Volume on Playback which:
* When playback is started in MC, it "remembers" the current System Volume level
* Sets the system volume to 100% as playback starts
* Re-sets the system volume to the previously set System Volume as soon as playback is stopped
This is very convenient for use with Internal Volume, because it allows you to set a (lower) System Volume for regular dumb applications like Web Browsers and whatnot that don't have their own convenient volume controls, but to still use MC's higher quality Internal Volume mode. It Just Works.
It would be great to get the same in the Mac version in Core Audio. Since Exclusive Mode in Core Audio doesn't seem to be able to (at least with my regular onboard DACs) block other applications from using the audio device while MC is using it, it won't be quite as "safe" as the Windows version, but it should still be pretty useful for most cases.
It'd be even more awesome if you could also...
Enable Do Not Disturb while playback is active