That wouldn't fix the situation at all...just add more voices and more frequencies and more people who must coordinate to prevent a runway incursion.
Runway incursions have been a hot potato for several years now (potatoe if you're Dan Quayle)...we're generally talking accidental incursions when someone taxies where they're not supposed to be. Confuse that by putting people intentionally on the runway to sit and wait, and the potential increases by a large margin.
Crossing train tracks is potentially dangerous...there's one place the trains congregate and travel, and that's on the tracks. If you're going to get hit by a train, it's going to be while crossing the tracks. Running through traffic on the highway is more dangerous than being off the highway, normally. Standing in front of a loaded weapon is generally a whole lot less dangerous than standing behind it, though weapons of serious stature kill in front and wound behind. Being on an active runway should be considered nothing different than being on the train tracks...spend as little time as you can there.
Unless I know I'll be rolling right away, I don't like spending any more time on the runway than I must. It's the one place that everybody intends to go on every flight it's potentially the greatest chance of having an incursion and accident, and one should minimize one's time there to the shortest interval possible. Avoiding positioning and holding accomplishes this just fine.
