OK. I've been going on about buttons many times. Here, for instance.
Nowadays I think this should be the best way of placing the buttons. The big button on the upper side rather than on top as suggested here will be as easy to find even when swimming or when skiing with gloves on. And gives more room for a big display. Never mind the hasty sketch :-) Start/lap/stopbutton:
Short press: start or lap.
1 sec press and hold: stopPoweroff/lightbutton
short press: light on/off
long press: overriding the lighttimer, keeping the light on until button pressed again
short press: goes through the different pages as usual
long press: jump to chronograph
menu+arrow up: preset shortcut of choice #1 (or better, shortcutpage as suggested by gerhard here
menu+arrow down: preset shortcut of choice #2
menu+escape: preset shortcut of choice #3