Hi all,
for those of you who might be interested, I initialized a schema plugin template [1] which could be used as a starting point for making iso19139 profiles following the good documentation [2].
Cheers.
Francois
[1] https://github.com/geonetwork/schema-plugins/tree/master/iso19139.xyz
[2] http://geonetwork-opensource.org/manuals/trunk/eng/developer/schemaPlugins/index.html