I lack an insider connection, but I don't think the elevators are on opposite sides. I think one is where we've all assumed it was, which will line up with the open hatch on the side of the walker from which troopers will fire down at us. There doesn't seem to be an opening on the opposite side for the vehicle to enter the second level. Also, in your diagram you show the elevator going much higher than I would expect. The showbuilding's second floor lies between the knee and shoulder height of the walkers.
I do believe there will be two lifts, and if we go way back through Bioreconstruct's aerials, we can see where they should be as there are two pits located at the edges of the AT-AT room:
View attachment 349154
View attachment 349155
If correct, this would put the second lift (green) facing the AT-AT's heads which would make for a dramatic and imposing view.