I was staying near a shopping/dining area near a rail station. You swiped your credit card when you entered and when you left. You got a couple of hours of free parking. I've been to other locations where parking got "validated" at the point of purchase. Instead of stamping your parking receipt an entry was made in the computer and the applicable number of free hours was automatically credited to you.Disney Springs station most likely won't happen unless they institute a parking charge for Disney Springs, or they only run the line starting in the late afternoon.
I suspect people parking at DS in order to avoid theme park parking are going to want to park for hours more then people visiting DS. A few hours free parking and generous validation should accommodate people who are avoiding theme park charges. Only issue would be if a drinking guest decided to Uber home. System could even waive those charges if your bar tab was large enough.
Years ago rumor was Disney was going to put a second TTC at DTD. Accommodate guests staying on I Drive. I don't think current garage capacity could handle significant theme park parking.