Trust me, there's plenty of space in there for a new room...its just that aah well, here goes my explination of the ride system...
Your elevator sits in a cage...the cage has a "guidewire" on it, similar to the type found in Universe of Energy, and maybe GMR. The guidewire emits and sends signals to and from each cage, and sends it to the RCC (ride control computer). If the RCC detects that a cage traveled off course, mainly due to a power glitch, it will stop the ride. 80% of the ride is going UP or DOWN. there's lots of space INSIDE between going up/down to add more stuff...remember, its 13 STORIES! the rooms are only in the 3 and 5th, i think, and then its all the way up with NOTHING there! so, it IS feasable, just probably very tedius, as the whole track and "cage holders" would have to be built and somehow transported through the tower to their respectave locations.
Ian