Mount Mitchell, NC: 6684 feet 
Mount Washington, NH: 6288 feet 
These eastern Mountains are indeed majestic, towering overhead when you look to ascend them. Mt Washington would stand in perfectly for Caradhras.
There are some examples of .mrules and other useful things for Maperitive.[2,3]
Also, on OSM wiki there are few pages useful for design rules for Maperitive.[4,5,6]
I suppose Mapbox could be created from that?