Haven't read the entire thread so I'm sorry if this was brought up already but why not just do 3 hour parking free. Anyone shopping or eating there should be fine with that amount of time. After that charge like $5.00 an hour. Anyone parking for a theme park will be paying a lot more than theme park parking lot prices and with having to take a bus to a hotel and transferring to a theme park, no one will even try it. If they do then Disney makes out. I've personally never parked in Disney Springs and gone to the theme park because transferring buses is just too annoying. I'd rather pay the regular parking price.
The tl;dr version is that it wont happen because the garage belongs to RCID. And a few other reasons, read what Steve posted on it.