Split idle-delay into 2 separate settings for different screen blank timeouts for ac and battery.
The setting org.gnome.desktop.session.idle-delay is translated in the settings gui as "Blank Screen" setting and is used as a timeout that results in turning off the display. This is one global setting that defaults to 5 minutes regardless of whether you are plugged into AC or not.
When plugged into AC, I never want the screen to turn off. I might set it to 2 hours just to avoid being wasteful, but it's not really necessary. 5 minutes is extremely annoying as it takes about 10 seconds for all my monitors to turn themselves on after I start moving the mouse around or hitting keys on the keyboard. But if I unplug my laptop from my dock, I'd like to use a short timeout like 5 minutes to avoid killing the battery.
I propose removing idle-delay and replacing it with idle-delay-ac and idle-delay-battery and reflecting these changes in the settings gui. This follows the same pattern as sleep-inactive-battery-timeout and sleep-inactive-ac-timeout.