A normal watch face sleeps after the display timeout [set by the user on the watch].
1) So any Toybox timers stop working and it's then not possible to wake the face. after a certain time or on need.
2) it's not possible to temporarily keep the display on for a few seconds more than the timeout.
2) It's not possible to put the watch face to sleep programmatically on user request.
[following a recent update - the watch face seems to stay on permanently if displaying a notification]
Using background mode creates other issues in that it may not sleep, so uses more battery
1) the display still can't be woken on a temporal event as it is already running
2) the watch face can't be put to sleep,
3) the watch face display can't be woken programmatically
Furthermore it seems a watch face cannot detect screen or button touch or make vibration or tones.
This presents severe limitations for designing a sophisticated watch face that's easy to use and functional.
I may be I missed some functions. Are there any examples that demonstrate solving any of these issues?