Yeah I agree!! I think to be honest, given the "entrances" that have been made, we'll be able to place our own. There's an archway which looks like a "Spawn Point" for guests and I absolutely believe in any kind of Scenario Builder, we can choose where that spawn point might be.
I think we'll be able to build our own entrances, or place blue prints of entrances at least. I don't see any reason why they would limit us to the prebuilt entrances which are made from the same scenery pieces as we have available to us.
All of the above is speculation of course, but I think building our own entrances which meets a number of set criteria (certain path width, certain distance to permiter of map etc) will work.