At the end of the day, I found that plantuml is the most suitable tool for this.Graphviz dot is interesting, but it doesn't feel natural to make class diagram with it, or at least it's less handy... I could bring several arguments to support this, but it's not the topic.Everybody wanting to try itself is welcome, but, *I* can take the commitment to maintain it over the years.
Here are the 3 svg files witch are my last proposals for the moment: