Why don't you use "Do not disturb"? It seems just what you need - phone can stay screen up, but won't make a noise or light up the screen. You can enable it automatically with a predefined schedule, or manually. And, with DnD, there is a possibility to still allow ringer for some select people or by repeated calls from one.
Yep.... I use DND between 23:00 and 06:00. I created a group called "DND Allowed" and added important numbers to this and allow this group to "break through" DND.
I still think there is a need for "Profiles" like back in the Nokia days, to allow quick switching of settings for when in meetings etc etc.