I mostly finished analysing how much it costs to me to keep the data up to date and rendering the maps. I will have to change the map design a little, but at the end the project seems useful. all the details in the following links:

http://www.grulic.org.ar/~mdione/glob/posts/appending-osm-data-with-flat-nodes/

http://www.grulic.org.ar/~mdione/glob/posts/detailed-osm-mapnik-redering-times/

You can see the rendered map here:

http://grulicueva.homenet.org/~mdione/Elevation.html