Finally got a chance to shoot some test footage, after making the decision to use the environment manipulation idea. The reasoning for this largely being that it would be considerably easier to find a location and control the shooting of a wall over a road.
Unfortunately the test footage isn't particularly useful, as there is far too much camera shake present. Looks like I'll need to find a way to keep the movement smooth.
Despite these short-comings, I've begun to put together a few animation test for the kinds of effects to be used in the film: