Editor can only add compound prototype root nodes

When adding a compound to a document what should happen is that the entire prototype of the compound in question should be copied. Say we have a compound at

/hippo:namespaces/project/compound

which has a prototype defined at

/hippo:namespaces/project/compound/hipposysedit:prototypes/hipposysedit:prototype

then the prototype node itself is readable for the editor but not any of its subnodes.
When a compound is added the required nodes are added in steps instead of all at once. So if the prototype node would have a subnode of type hippostd:html for instance, the hippostd:html node is added not on the basis of the compound prototype but on the basis of the prototype at

/hippo:namespaces/hippostd/html/hipposysedit:prototypes/hipposysedit:prototype

The problem is that the entire compound graph is not added based on the compound prototype, but based on the prototypes of all the different types making up the compound.

This problem does not occur when adding documents because this is done as a workflow action using a workflow user session which does not have restricted read access. So one solution to this problem could be to make adding a compound to a document a workflow action.
Another possible solution is to make /hippo:namespaces readable for all users based on a hierarchical constraint. As schrijvers pointed out though, there are projects that use access rights on templates to prevent certain users to be able to edit some document fields.