I spent a couple of hours on this and it’s unfortunately not easy either.
The plugin outlet is implemented as keyword that basically does the same thing as the partial tag in ember that hoists a block into the upper template, except I hoist a template we’ve declared as a connector.
Now of course I can conditionally do that, however it seems that I can’t access the scope of the keyword (or I can’t figure out how to anyway) because everything in ember is based on streams of dependencies that are passed into things.
There doesn’t seem to be any easy way in a keyword handler to call this.get('model.solved_count') 
If you’re feeling adventurous and think you can figure out something in Ember’s API to do this, here’s my work:
https://github.com/discourse/discourse/commit/7b8e4a7110df1c40fa952df5fe216d844fbecc9d