Allow Engagement Content Streams to include multiple smart campaigns from a Program. In other words, add "Smart Campaign" as a Content Type and the Smart Campaign could be from the same or different Program as the one used elsewhere in the stream.
Right now, it seems like one has to create a unique Program and associated smart campaign for every personalized content (white paper, webinar, etc.) to be sent to the lead (based on their industry, demographics, activity, etc.). That's too much overhead.
I read somewhere that the Program membership is used to verify uniqueness of content for Program Type content. I guess by the same token (no pun intended), you could use Campaign membership as the criteria to ensure unique sends.