I just sent a simliar request to yours from 2018 and you got 110 upvotes I wonder how many it takes to get an idea implemented at Hubspot.
Here was my idea submitted today. I really love the idea and found your post after I had submitted but I think our thinking is similar.
Team: Marketing Team
Goal: Being able to reach out to the most engaged contacts over time
Value: By knowing who is engaging with us the most over time, that is, those who open, reach and click on our emails, we will be better able to reach and communicate with them by offering value-added content and ideas for them.
We have been sending marketing emails out for almost two years. I searched on HubSpot for a way to find out over time who are our most engaged contacts, not just by individual email but through the course of the emails we’ve sent in an all-encompassing report. I couldn’t find such a report on HubSpot and was told that I can only look at analytics by each email we send but not in total. The HS rep told me to submit this idea to HS community ideas so the engineers can give it a look and maybe implement it in the future.
I am looking forward to hearing from others about this issue to see if anyone else has this need. Imagine, being able to know over time who likes and reads our information! And then being able to reach out one-to-one to see how else we can help them. 
Thanks for helping and for your ideas!