TL;DR: We do not support having the dev_appserver use the real app-engine datastore. Even with the suggested use of "remote_api", AFAIK, the dev_appserver does not know how to use it.
If you really want to make this work, you could write your own low-level API and have your own datastore abstraction that uses your API instead of the actual datastore, however this is a non trivial amount of work.
Another option is to have a servlet that can pre-populate your dev datastore with the data you need from checked in files. The checked in raw data could be non-real data or obfuscated real data. At dev_appserver startup, you hit this URL and your database becomes pre-populated with data. If you take this route, you get the bonus of not operating on your live data with dev code.
HTH!