Unfortunately there are no other method currently avaible in MED.
See my discussion with @jcl about this here, so we are left with manually lowering the terrain.

To get what you want i L3DT, work with the Design Map.

Tip

Start with a flat terrain ( assign Altitude=0 rel=0 and Apply all).
Then paint your mountains and hills by setting Altitude=1 rel=1 and paint until
you get what you want. Each stroke will add a small bit of height. I have found
that building hills up is better than setting the height in one step. But thats a
matter of taste.

Recalulate and redo if not satisfied.

Then decorate with Erode at the hill sides if you want to.
Terraces can work for your roads.

Making really flat roads may need another techniqe as
adding the as models in WED.