I have lost counts on how many times you have sugested the "vitual viewpoint technique" as an valid solution to a tecnical challenge. Could you please go out and try the theory in real life before you surgest it next time to someone in here - please try it with a 3d object, like a brigde or a building, not a flat wall.
I can tell you from experience through my daily work, that if you move the lens, you will cretate a new perpective of the object, so you will end up with a series of images, each with there own unique perspective. No amount of shift is going to change that.....
I am waiting for a sliding back I bought on eBay, and this should enable me to do this (my Silvestri back is not worth using, as it does not focus, and the digiback falls out).
Viewpoint is perspective, they say, so if a series of photos has the same (virtual) viewpoint, they should all have similar perspective... but where you want to join the pictures the perspective/parallax would be different.
The way round the perspective problem is to join the pictures in flat areas of the subject... this would be very easy to do on a typical building with rows of windows, and, as you suggest, the technique would not work for complex 3D scenes where you could not join pictures on flat surfaces.
... and old buildings with inset windows, bay windows, porches etc. are not totally flat.
... many stone arch bridges would also be easy, as the pictures can be joined between the arches.
I appreciate that the technique would not work for a typical landscape... but I want to take pictures or harbours, and at Swanage and Port Isaac there are roads on which I could join the pictures ( I am thinking of using pan-and-stitch for some sections of the pictures, and shift-and -stitch and/or virtual viewpoint for others).
Most rural stone brides would be relatively easy, as they have flat areas between the arches.
The "real world" Seitz sample picture in this topic would be difficult or impossible...
You would have to be in the river to take the pictures
There are not large flat areas between the arches
The building in the background (The UK Houses of Parliament, or Palace of Westminster) would be at a larger scale than in a picture taken from the virtual viewpoint, so a simple join between the arches of the bridge would mean that you would loose some bits of the building, or do a complicated stitch, re-scale and re-combine operation which might work, but would be a PITA.
There is nothing miraculous about the technique, and it may well not be suitable or possible for the bridge project that is the subject of this topic (access tends to be a problem for bridges)... but, for a typical wide building in a narrow street I think it would work.