I would want this too.
(Correct my other watch's users if I'm wrong).
Currently (unavailable) used tap gestures:
1) 3x tap - open faces menu
2) long press - changes used face program
3) top to bottom shift - opening watch settings
4) right to left - opening apps menu
That gives us available:
1) one tap (in general, or in different places)
2) two tap (less likely - even I don't want this)
3) bottom to top
4) left to right