Any chance we could use a namespace definition URL etc for adding a vocabulary, rather than downloading it, and uploading it again to add a new vocabulary? I appreciate the need for custom vocabularies, but I find it puzzling in terms of LOD why uploading a local file is the only option for adding a new vocabulary to Omeka S.
You can post an issue on the github page of the project, it will have more chances to be implemented, than lost here.