What if core subscription let you play up to level 10, only against bots?
1) It's an additional enticement for non-subscribers to buy core subscription level.
2) It offers a migration path for core subscribers to move to 'complete'.
Summary: good for the subscriber, and good for Shuffle IT. Win-win.
P.S. It could also be offered as an option on 'core' for .50 Euro more, say.