I suspect that I know the answer to this question, but...
I tried making a smaller version of LandscapeLeft skin, but ended up confounded by the fact that all of the Key descriptors have to be redesigned for smaller size and different position... that's well beyond my motivation factor!!
I think I see, now, why so many skins are the same size as other skins...
A skin editor would be a *ton* of work, especially if it needed to be cross-platform, but that seems like the only way to manage this task...