A heavily work in progress gate model; it's not perfect, but it can get your park's land cruiser through fences.
When buildings are attached to fences the collision for the fence piece stays in place. This means a true gate likely isn't possible. However, you can drive the Land Cruiser into this invisible wall, abandon it and then jump back into it and the game will usually push you through the wall to the other side of the paddock. You may need a few attempts to line the vehicle up correctly but it isn't a precise position; you do need to enter from the longer side (the side where the cruiser would exit from in the original model). From my testing dinosaurs are not able to clip through this invisible wall thus the gate can function as intended (no need for avoidance beacons).
Currently I have not been able to get the animations of the doors opening and closing to work with this setup. I'm also looking into this as even though it isn't going to help the function it will look better than having the cruiser clip through the gate doors.
Installation: Back up your files first and then place the Data folder of this mod into your JPOG Data folder. Overwrite the files and you're ready to go.
Update: If you installed prior to this update, revert your files before installing this new version. This update will not be able to overwrite the old version.
Credits: Thanks to Who D Matt for figuring out a way to get the gate into the game without needing to sacrifice the Viewing Vent!
Video showcase: