Ok, what if the backward launch is through a hole the the bottom center on a large domed screen. Similar to being launched backwards through the screen in Gringott's.
The opening scene would be the scene with a Groot AA and a screen with Rocket outside in the ship. All of that is in front of you. The big domed screen that is above and behind you is showing the inside of the room that you and Groot are in. Someone, activates that wormhole jump thing and starting directly behind you and moving forward, the whole room starts to whirlpool. Just as the whirlpool is directly above/to the side of the train you launch backwards into the vortex. The swirling projection continues around you through the launch tunnel into the big dark gravity building where things get weird.