Hey so I work at Lagoon in the rides department and had the same question as you, so I asked a supervisor and the door is there because if one of the motors or plcs for the lift system in that tower goes out the only way to replace it is by crane. There are two cranes in the motor room at the top of the tower, one is used to move the motor or plc over from it's place to the space directily in front of the door where the other crane is used to lift it out of the door using a pivoting motion at which point a third crane would have to be moved onto the park to grab the motor and bring it down. Also I believe that is how they got the motors in there to begin with.