Games Workshop Digital has chimed in on what size of foritifications can be used for Void Shields. This was very similar to the direction that I was thinking. Void shields require an impassible fortification with battlements, and while we have plenty of freedom with which to be creative, its nice to have some guidance in the probable event a model is released for these.
Of course I think these are great additions to the game, and a fantastic counter to alpha strike armies, so I am very interested in creating my own. For now though, I will use my gun batteries without the guns.