How to keep a window from stealing focus in GNOME Shell

I've got multiple workspaces and two monitors in my GNOME Shell, and I'd like to find a way to exclude a window on my secondary monitor from ever stealing focus. Ideally, it'd be nice to exclude these windows from Alt+Tab as well.

A really good example of how this can get in the way is the following setup:

   Primary      Secondary
1: Thunderbird  system monitor
2: (nothing)    system monitor
3: Terminal     system monitor

In this situation if I'm reading my mail in workspace #1 and switch to workspace #3 (terminal) to do something and then come back, my focus is now on the system monitor and not on Thunderbird.

I'm unaware of any extensions that can fix this, but if one does exist or if we're just talking a change to dconf or something, I'd be happy with that. If however it turns out that this is currently impossible in GNOME, then I'd like to know that too, just so I can report it as a feature request.