Maybe you can help me figure this out. There doesn't seem to be a perfect option at the moment. You can't use capsule items in map view, so it's not as simple as changing the existing winch's capsule_range parameter.
Option 1: Change the winch to a "selection box" tool. You can click on things like normal, but if you click and drag you get a box which is confusing. It would have to display an error if too many things are selected at once.
Option 2: Make Spidertrons automatically load themselves when they finish a move standing on top of a vehicle wagon. Then make them automatically unload when a train gets to station with a signal? (You can't get any events from un-paired spider remotes to trigger unloading.)