This is something you can solve on your own. I'm not sure which developer you're referring to when it comes to this airplane, and I'm guessing it's not supported by GSX by default. If you customize the GSX aircraft configuration, you can set the door, so it has its own embedded stairs. That should make it, so the stairs don't show up. As for the luggage, it looks like the belt loader needs to be repositioned a little bit, as it looks like it might be partially inside the airplane.