I believe this would have a performance boost marginally. Normal maps can pop out relatively close without noticing too much. It all depends on the distances involved for each stage. The penultimate stage could have its normal removed aswell.
Since lodded materials are still normal material like any other mesh, they can even have an entirely different shader.
Note: All materials have a distance in which they switch back into a basic mode that keeps up performance. Be careful with lodded materials as you may only ever see the basic if the distances are not set
There are many performance techniques we need to implement into skyline. We are still in beta and have not yet started on the performance enhancements and resource unloading is currently one of those features. We reckon that once the performance features/tweaks are done, we should be able to run large open worlds with a half decent framerate but without the loss of quality.