If you have two building designs for the same site, you can avoid multiple site models/building models scattered around your model environment by creating two new layer combinations.
First create two new layer combinations module option A & B, then three new layers. The first is the “modules layer” which contains all common hotlink elements.The next two layers are the toggle layers, one is only on with layer combination “A”, the other only layer combination “B”.
The last step is to assign hotlinks to one of the toggle layers (I learned something new about this today!). First select the hotlink to be assigned to toggle layer A, go to File > External Content > Hotlink Module Settings.
Change the Master Layer for this module to the correct toggle layer and follow these steps for each module which will be part of the option A or option B schemes.