I thought to create a plugin to automatise the creation of new taxonomies like the 'Add Category' panel in the admin area.
But it is better if something is integrated in the next releases or versions.
I thought on a Admin Panel - with a menu point 'Create Taxonomie' - on which a user can create a taxonomie and hierachical items.
then those taxonomies are accessible on each post page.
I can develop by myself a plugin for that, but I thought if in future wp offer it, the work is for nothing.