The ramps would have to be built individually, otherwise you might end up with something odd with the smaller sections of ridge where the ramp you want to place is 'too big' for that area. Also, this would stop those annoying "hey guys i just claimed myself a giant-ass valley; now you'll have to walk around!"
Of course, given that we can make ramps, maybe we could also make ridges as a 'structure' that's able to decay, too? After all, a ridge is just a ramp in reverse.

Thus you could simulate a fortress on top of a man-made hill that will gradually decay back into flat land.
The Dwarf is making a plaintive gesture. He doesn't really care about anything any more.