An option to view more activity from all of a company's contacts directly on that company's page.
For instance, an option to be able to see Mailchimp activity/any marketing emails sent to contacts straight from their company's page. Just like how 1:1 emails and notes can sync between contact/company pages, this would simply expand upon the information we can see/filter on a company page.
With the ability to filter these kinds of activities that would be showing up on the company page, I think it would just be helpful overall when multiple users are doing a lot of different things in HubSpot relating to entire companies. Maybe one user wants to be able to see just the marketing email activity for companies, while another user wants to see how certain integrations are performing with all of a company's contacts.