One thing I would like to see is a bio card deck. Each time a slave reaches Canada or is lost (killed), you draw a bio card and learn about the person you helped or could not help. While this would be a heavy option for some, I think making the struggle more humanized would result in more weight given to your choices.
this is an amazing idea!
did you propose this to the publisher?
Even if you didn´t use this deck when playing just knowing it exists would make the game much more powerful.
Maybe they could be convinced of producing a mini expansion together with the kickstarter add ons.