We have a very similar use case. We got rid of our external server (with clip,zip & ship function) and moved our data to ArcGIS Online and implemented Open Data for our public datasets. However, we also had some data which was restricted access so we setup a new ArcGIS Online group and accounts for a handful of externals to access this data (they're too small to require their own ArcGIS Online sites or have alternative GIS software in house). We assumed level 1 licenses would be fine as the documentation (Use layers—ArcGIS Online Help | ArcGIS ) has no mention of the need for Level 2 licenses! Needing to grant Level 2 licenses for a user to download a shapefile/json/fgdb, once a month or less frequently, is a waste of a license and fairly absurd. It should be a direct download as not everyone wants to use it in an Esri webmap/application and it could be implemented very similar to the way Open Data does it for public layers.
An Idea very similar to the improvement suggested is here Download data to computer from item details page - without needing an AGO account - I suggest you add your vote to it.
Kelly Gerrow to answer your questions:
Can you provide some more information about your workflow?
Workflow as above - restricted data held in a group for external users to take an extract for their systems. Unfortunately not everyone is in the realm of mashing up services/sourcing them directly due to technology/security considerations.
What is the data? (brief description would be great)
Access Tracks (polylines) - some of which are over private land.
What is the level 1 user going to do with the data? (use it in ArcGIS Online or download a CSV for other purposes?)
Use it outside of Arc products for their own systems.
Are your users looking to export the entire dataset or a subset of the data?
Both - most want the whole dataset but some would prefer a subset. Could start things off simple with whole dataset downloads and then implement the smarts for extracting subsets.