Looking for enhanced Engagement Program logic to weed out non-engagers

Most of the people that become members of our EPs are due to prior behavior that relate to the content within a specific EP.  What we would like to do is prevent people - who haven't shown any engagement over a specific period of time/casts - from receiving future casts.  Aside from creating custom score fields (each time someone engages) that would allow us to trigger off whether or not a value exists, are any of you doing this today using creative filtering techniques?  And yes, we do use child programs within our EPs (vs. just simple emails) so that we can include smart list criteria to ensure a lead is qualified to receive a specific cast.  But we need to be careful here due to this limitation: If a lead doesn't qualify for an Engagement Program cast, does it proceed to the next email?

I suppose one tactic would be to create additional streams that contain the longer-term content.  And people transition from one stream to the next as they show engagement.  That would require duplicating the content in every stream to ensure they receive all content.  For example we can have one stream that has 4 pieces of core content.  And then if they engage with either of these (clicks link in email), they are pulled into a longer-term nurture stream.  This longer term nurture stream would need to included that core content for those users that prematurely got pulled into the this stage (so that they continue to receive the initial "core" content).

I'd be interested to learn how others are using EPs to ensure longer term casts are only being sent to those that are actively engaged.