Yeah that makes getting the message correct kind of difficult.  If you're going to leave normal attributes but remove persistence then a lot of people who are using normal attributes are using them 'correctly' for the future use case which would not be deprecated.  We only want to deprecate the people who are using them correctly now to save persistent data.  Can we determine if someone accesses a normal-level attribute without first setting it and only issue a warning in that case?  I think its possible, but somewhat annoying code to write?