Perhaps it could be used by GO as an Milton Express train?
There are enough tracks on Lakeshore West line for Express service out of Union.
Maybe this way an express Milton GO train could head down the Lakeshore West Express trackage, and bypass Kipling station?
It could also take relief off of the Georgetown South corridor, which has to handle UPX, GO Barrie, Kitchener, Milton trains, and soon Smarttrack.
Maybe every other Milton train could bypass Kipling station and shave off some minutes for commuters.