Maybe I wasn't clear, but I want to limit the rights, rather than extend them, so I don't need content/create, and I want the translator to only edit text, not object relations. Content/edit is needed to translate/edit text fields, but it also allows creation/deletion of object relations, that's what I want to prevent.
I'm not talking about attribute relations here, but object relations on the object level, as specified in the Related Objects section at the bottom of the content/edit view.
In my opinion, to create translations of existing objects, the user should not need the content/edit function, just the content/translate function. But how it is setup in 3.8, translating content is done in the content/edit view, so a user who is doing just translations of existing objects also need permission for edit, and thus enabling creation/deletion of object relations.
So, it seems object translation is seen (by eZ publish developers) as an extension to object editing, rather than as a limitation, which would be more logical, in my opinion. I wonder how other creators of multi-language sites think about this.