Your integration with Outreach is incomplete. A significant value of Outreach (and any email automation platform built for sales and SDRs) is logging opens and clicks on emails sent through Outreach. As of right now, these activities are not fed into Engagio to affect minute scoring, but it should be!
I know your recommended solution is to create a new activity type that logs the open and click, but this is not scalable or a feasible solution for most clients. It creates a massive amount of activity records in a client's salesforce org as an email could be opened 20 times. I now have 20 activity records created and logged to salesforce to show those opens. This will consume a lot of salesforce data storage, and also make it very difficult if I ever need to review email activities since I'll have all these open and click records mudding up my salesforce org.
If you have a full integration, then complete the work and build out an integrated solution that allows Engagio to see the Outreach activity in the single salesforce record outreach creates for the email send.