Ok, I submit a few pictures to help us figure out what this may or may not be.
First up, this picture from the holiblog:
http://www.holidayworld.com/holiblog/uploaded_images/21006VoyageAerial-740152.jpg
Obviously, that was during construction of the Thanksgiving area, but you can see that the lift hill goes up at an angle to the employee parking lot. So, unfortunetly, we can't completely rule out an expansion to the parking lot, or maintenance building/warehouse on the edge of the parking lot, because if it was built on the northern edge, it'd be awfully close to the picture paula posted.
But, in response to that picture:
http://www.holidayworld.com/images/ThanksPlan.jpg
Now, of course this picture is even older, and they did not build like this - they obviously decided that putting the dark ride next to the parking lot allowed them to build a 2 story building with workshops below - more bang for their buck. However, it does show the idea of Thanksgiving being expanded ..
-Chris