Huh, I never thought of it that way but we sort of have that, just that it's two entries instead of a whole list of frequencies. There's a general chat that you can read whenever~never (participate as much as you want), and one that you are supposed to read (also after a holiday, you're meant to read what was announced). Taking a peek every now and then throughout the day is fine (most days there's 0-2 messages in it). It's basically email whereas the other chat is 'chat'
And of course, if someone needs you specifically, they'll @mention or PM you
Not sure why you would need a four-tiered scheme of frequencies for this