Andrew,
To your second question, the answer is yes. N1QL-created views can be accessed via the client SDK and the REST API.
To your second question, it depends on the existing views. If the view has a map function that emits a field and a document id, and the view has no reduce, then it may be usable. The view’s name would also need to match the convention that N1QL uses internally to identify indexes.
Thanks.