There are lots of little customizations and improvements one could imagine for the various watch faces, but the want of a combined complication for the timer and stopwatch frustrates me almost every day. There are any number of ways this could be implemented. Here are two.
In the simpler version, the stopwatch complication works exactly like it does now, except that it shows the timer when the stopwatch isn’t running but a timer is running. When neither is running, it shows the 00:00 stopwatch. Conversely, the timer complication shows the stopwatch when there’s no active timer but the stopwatch is running.
This would require zero interface changes and would, I think, genuinely delight users.
A slightly more ambitious implementation you might call a flex complication: the users sets a default mode for a complication, such as alarm or weather. The complication shows that most of the time. Whenever either stopwatch or timer is running, the complication simply switches to stopwatch or timer. (I would suggest favoring timer if both are running, but Apple could go nuts and make it a setting.)
I think this would make the watch face a hundred times more useful, and would keep me from having to switch faces so I can see my timers and stopwatches without having to look at a 00:00 all the time. With watchOS 3 it’s painless to start the stopwatch and timer from the dock or the home screen.
Bonus: I sometimes wonder why stopwatch timer, and alarm aren’t rolled into one app. They have this inherent complication synergy, but even the apps could be combined (just let the user swipe left to right between the three screens) and having two orange dots fewer on the home screen would be a win.