I recently used iCopy in a project I was undertaking specifically because of the fact that the copies I was making just varied in one size and that change was the height of the object. All other dimensions were constant.
In this instance I was only changing one part but with iCopy you can configure whole assemblies as long as the sketch that you are using is adaptive.
Adaptive technology is something that Inventor has had for years ( well ever since I started on Inventor v5.3). It allows parts to change adaptively to the parts surrounding it.
Think of a shaft and a bush. With adaptivity you are able to drive the diameter of the bush from the diameter of the shaft but not having to use any linked dimensions for either part.
Adaptivity can be an absolute gem of technolgy in the software but please be warned if not planned in advance and efficiently things can go very wrong.
Another modelling technique that iCopy utilises is skeletal modelling. This is a Top Down modelling technique.
With skeletal modelling you will drive the geometry of all your components that you want in your assembly. This in turn makes it very simple to change parts in an assembly and not worry about constraints failing or parts not being able to be generated.
Your one skeleton model will drive the changes that you make into the assembly components.
This is wonderful when troubleshooting as well as you do not have to open a million and one parts and drive down into the sketches to find out what is going wrong.
This one skeleton file will rule them all.