Earlier quoted context omitted.
But this isn't adequate for the IM use case at all? I spend the bulk of my time not focused on my chat app tab(s) but I definitely want to be reported as 'available' by those chat apps, because I am if someone messages me.
So after 20 minutes instead of logging you out the away status is set. Not sure I understand your special case here.
If I go out for a walk or I go watch some TV or otherwise stop using my computer, depending on the chat app I want to either automatically be 'unavailable' (for work chat app), or I want to stay 'available' but have notifications go to my phone instead of the chat tab (for friends' chat apps).