I have an idea which is both useful for users and would increase WP profit.
The idea is simple: Provide a list of all themes available on WP with popularity percent for each theme. List the least popular themes first and recommend to the users to use the least popular themes advertising it as "staying out from the crowd".
Then the users will have incentive to use paid (and therefore less popular themes). It will increase your profit.
This will also increase diversity of the Web and is good for everybody.