It would be nice if there was a way to shear a static mesh (even if limited to shearing along the z-axis). This would be extremely useful for doing things like railings and fences that need to follow a sloping terrain while keeping the posts vertical.
In the cases you describe a Spline Mesh works ideal for that already:
Splines don’t keep posts vertical. Plus, they are a nuisance to use.
Well, they do, if you make them to 
What kind of nuissance are you referring to ?
They do if you limit edge loops along your mesh. Also they’re fairly simple to build, I actually just wrote up a tutorial on them, it’s in my signature.