If you develop a non iOS peripheral, then you should be able to start acting as ATT client once the iOS central connected to you. The ATT database is shared accross applications and should be accessible this way. You can initialize it in a separate app or in the same app using a CPBeripheralManager.
Otherwise, there has been no indication from Apple that they would be considering this use case so I wouldn't expect it be implemented in the foreseeable future.