I want this too! I nearly always want to trim the first few minutes and the last off my workouts. I often have to start the watch, then put my classes away, lock the car, lock the watch display, put my gloves on, etc., and then my friends aren't ready, the whole deal can take several minutes. Ditto when I get back, and of course I often get new records when I drive away after a run and hit 60km/h.
Give me the ability to trim off the ends of the workout and have the statistics all apply to only what is left. I would be so happy :)